Mboard tshooting

28 MOTHERBOARD TROUBLESHOOTING

CONT CO NTEN ENTS TS AT A GL GLAN ANCE CE Active, Acti ve, Pa Passi ssive, ve, and Modular Modular Understanding the Motherboard Socket 7, Socket 8, or Slot 1 AT, ATX, and NLX Learning your way around

Troubleshooting a Motherboard Repair vs. replace Start with the basics Symptoms

Further Study

The motherboard is the heart of any personal computer. It provides system resources (i.e., IRQ lines, DMA channels, I/O locations), as well as “core” components, such as the CPU, chipset(s), Real-Time Clock (RTC), and all system memory—including memory—including RAM, BIOS ROM, and CMOS RAM. Indeed, most of a PC’s capabilities are are defined by motherboard compocomponents. This chapter is intended to provide a guided tour of contemporary motherboards and show you how to translate error information and symptoms into motherboard repairs.

Active, Passive, and Modular Before going any further, you should understand the difference between a motherboard and a backplane. backplane. For the purposes purposes of this book, a motherboard is a printed circuit board that contains most of the processing components required required by the computer. PC purists of938

UNDERSTAND UNDERSTANDING ING THE MOTHERBOAR MOTHERBOARD D

939

ten refer to a motherboard as an active backplane. The term active is used because ICs are running on the board. The advantage of a motherboard is its simplicity—the motherboard motherboard virtually is the PC. Unfortunately, the motherboard has disadvantages. disadvantages. Namely, it is difdifficult to upgrade. Aside from plugging in an upgraded CPU or adding RAM, the only real way to upgrade a motherboard is to replace it outright outright with a newer one. For example, the only way to add PCI bus slots to an all-ISA motherboard is to replace the motherboard with one that contains PCI slots. On the other hand, a backplane (also referred to as a passive backplane) is little more than a board containing interconnecting slots—no ICs are on the backplane (except perhaps some power-supply regulating circuitry). circuitry). The CPU, DRAM, BIOS ROM, and other central-processing components are fabricated onto a board that simply plugs into one of the backplane slots. Other expansion devices (e.g., (e.g., video board, drive controller, sound sound board, etc.) just plug into adjacent slots. slots. The PS/2 was one of the first PCs to use a back plane design. design. Backplane systems systems are easy to troubleshoot. Unlike traditional traditional mother boards, which require the entire system to be disassembled, a processor board can be removed and replaced as easily as any other board, so it is also a simple matter to upgrade the PC by installing a new processor processor board. The great limitation to backplanes backplanes is the bus. Where traditional motherboards can optimize a system with different busses, the back plane is limited to a single bus style (usually (usually ISA or MCA). High-performance bus architectures, such as VL or PCI, are not readily available. In an effort to provide a motherboard that is more upgradeable and serviceable, manufacturers are experimenting experimentin g with modular motherboards. The modular motherboard places the CPU, math co-processor, and key support ICs on a replaceable card that plugs into a motherboard. This, in turn, holds BIOS ROM, CMOS RAM, DRAM, other system controllers, controllers, and bus interfaces. The modular approach allows a motherboard to be upgraded far more than a traditional motherboard, without having to replace it outright—the replacement processing card is then much cheaper than a new motherboard. motherboard . However, today’s PC architectures can usually support a variety of CPU versions and an extensive amount of RAM on the original motherboard, so “modularity” has never become a very popular approach. Contrary to popular belief, expansion bus connectors are not needed to make a mother board. You can see this in any laptop or notebook computer motherboard (Fig. (Fig. 28-1). The devices that traditionally demanded expansion slots (video and drive controllers) are easily fabricated directly directly onto the motherboard. Even the motherboards used in most desktop and tower PCs over the last few years integrate video- and drive-controller circuits. circuits. If upgrades are needed in the future, the motherboard-based circuits can be disabled with jumpers, and replacement sub-systems are plugged into expansion slots.

Understanding the Motherboard Before you can troubleshoot a motherboard effectively, it is important that you know your way around and be able to identify at least most of the the available components. Although each motherboard is designed differently, this process of identification is not nearly as difficult as it might sound. This part of the chapter will familiarize familiarize you with the essential functions and components that you’ll find on a modern motherboard.

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S Y S T E M D A T A A N D T R O U B L E S H O O T I N G

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MOTH MOTHER ERBO BOAR ARD D TROUB TROUBLE LESH SHOO OOTI TING NG

BIOS ROM (IC19)

UART/Parallel (IC27)

Regulator (IC45)

Comparator (IC42)

dc-dc converter (IC43)

EMS memory (SIMM) socket (CN1)

EMS control (IC20)

CPU/system control (IC2)

FDC (IC39) LCDC (IC35)

CPU(V20) (IC1)

VRAM (IC33,34) EEPROM (IC31)

DRAM (1M-bit) (IC11-14)

FIGURE FIG URE 2828-1 1

DRAM (256K-bit) (IC16, 18)

DRAM (256K-bit) (IC15, 17)

Motherboard assembly for a Tandy 1500HD laptop.

Keyboard controller (IC21) Tandy Corporation

SOCKET 7, SOCKET 8, OR SLOT 1 When examining a motherboard, you’ll probably find it designated as “Socket 7,” “Socket 8,” or “Slot 1.” These classifications refer to to the type of CPU that the mother board can support: Socket-7 motherboards are generally designed for Pentium and Pentium MMX CPUs, Socket-8 motherboards are made for PentiumPro CPUs, and Slot-1 motherboards are slated for Pentium II systems. This does not mean that a mother board can support ANY such processor, only that the motherboard supports a given “class” of processor. For example, older Pentium motherboards can only support support Pentium CPUs up to 120MHz, but newer Pentium motherboards can support Pentium (or Pentium MMX) processors up to 200MHz—but all would be categorized as “Socket 7” motherboards. You can find find a complete breakdown of socket/slot designations designations in Chapter 11.


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AT, ATX, AND NLX Another important classification that you must be familiar with is the motherboard’s form factor is little more than the dimensions dimensions of the board factor. In simplest terms, the form factor and its mounting-hole positions, as well as the general layout and placement of key com ponents such as the CPU, SIMMs, SIMMs, and expansion slots. Today, the three major form facfactors to consider are: AT, ATX, and NLX. It is important for you to understand that form form factors do not directly influence performance—a “baby AT” motherboard and an NLX motherboard can offer exactly the same performance performance characteristics. Form factor is most important in system assembly and access for service. AT-style motherboards The “AT-style” motherboards really represent the classic ap proach to component placement (Fig. 28-2). 28-2). AT-style motherboards are typically typically available in two variations: variations: the “Baby AT” and the “Full “Full AT.” Both variations simply simply affect the overall dimensions dimensions of the motherboard (Full AT motherboards motherboards are larger). You can usually identify an AT-style AT-style motherboard based upon two distinctions. distinctions. First, look at the power connectors where the the power supply attaches. attaches. An AT-style motherboard uses uses two sets of 6-pin in-line connectors. connectors. Second, the CPU is usually positioned in line with the ISA bus slots (almost always obstructing full-length ISA cards).

The Socket-5 connector shown in Fig. 34-2 indicates an i486 motherboard.

“ATX-style” motherboards are the result of the first serious industry push to “standardize” the dimensions and connections of a PC motherboard, such as the ATX Slot 1 motherboard (Fig. 28-3). An ATX motherboard is distinguished distinguished by three points. First, all I/O port connectors are concentrated into into a single “I/O panel” at the rear of the motherboard. Second, the ATX motherboard motherboard uses a 20-pin 20-pin PS/2-style power connection from the power supply. supply. Third, the CPU is located clear and and away from all expansion bus slots—eliminating slots—eliminating any interference with full-slot full-slot expansion cards. ATX motherboards can be found supporting Socket 7, Socket 8, and Slot 1 CPUs. ATX-style motherboards

NLX-style motherboards Although ATX motherboards represented a good effort at

standardization, they still retain all the assembly problems of AT-style motherboards— namely that the motherboard is cumbersome to install and time-consuming to upgrade or replace. The “NLX-style” motherboards (Fig. (Fig. 28-4) overcome this disadvantage disadvantage by making the motherboard a replaceable “card,” and moving all expansion slots and connection headers (e.g., speaker connector, power-switch connector, connector, etc.) to a “riser card.” The NLX motherboard itself then plugs into the riser riser card. In this fashion, the motherboard motherboard can quickly and easily be removed from the system to change jumpers, add memory, or install a replacement motherboard.

LEARNING YOUR WAY AROUND Now that you’ve seen some essential motherboard classifications, classifications, it’s time to actually look at a motherboard up close, and identify the crucial crucial parts. For the purposes of this book, the

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Megatrends

Megatrends

FIGUR FIGURE E 28-2 28-2

The AMI Atlas PCI motherboard.

s d n e r t a g e M

American Megatrends, Inc.


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ATX I/O connectors

PCI slots ISA slots

Slot 1 CPU connector

SIMM/DIMM slots

2 Megatrends

FIGURE FIGURE 28-3 28-3

An Intel ATX Slot 1 motherboard.

Intel Corporation

NLX I/O connectors

NLX card edge connector

SIMM/DIMM slots


Slot 1 CPU connector

An Intel NLX Slot 1 motherboard.

Intel Corporation


944 944


Intel PD440FX ATX Slot 1 motherboard motherboard (Fig. 28-5) is used as a model. Other mother boards and form factors will appear a bit different, but the basic key parts are all the same. The pinouts of each major connector are illustrated in Fig. 28-6. The following chipset components are presented for for example purposes only. Your motherboard will undoubtedly use different chips (and chipsets)—each offering their own set of characteristics. 1 ISA bus slots For ISA adapter boards. 2 Yamaha OPL4-ML This optional on-board wavetable synthesizer features the single-

chip OPL4-ML (YMF704) IC. The OPL4-ML integrates the OPL3 audio system, general MIDI processor, and wavetable wavetable ROM into into a single component. The features include: general MIDI system-1 compliance, an interface compatible with MPU-401 UART mode, FM synthesis that is compatible with the OPL3 audio system, and wavetable synthesis generates up to 24 voices simultaneously. 3 Yamaha OPL3-SA3 This optional on-board audio subsystem features the Yamaha OPL3SA3 (YMF715) IC. The features include: a 16-bit audio audio CODEC and OPL3 FM synthesis; an integrated 3-D enhanced stereo controller including all required analog components; an interface for MPU-401 and a joystick (game port); stereo analog-to-digital and digital1

2

3

4

6 7 8

5

9

31 10 11 30

12

29

13

28 27

14 26

15

25


24

23

22 2 1

20

19

18

An Intel PD440FX motherboard layout.

17

16

Intel Corporation


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2 Telephony J2F3

J2F1

13

1 4 Telephony

PCI connectors(4) J4C1, J4D1 J4E1, J4E2

J2F6

Wavetable 8 2 7 1 J2F2

1 4 CD-ROM audio

ISA connectors(3) J4A1, J4B1

Slot 1 processor card connector

J1F1

1

J6M1

4

11

1

20

10

J4A1

Line in

J4B2

J4F1

3

1 Fan 3

Power J6C1

2

Chassis security

Bank 0 DRAM ( J6J1, J6J2) Bank 1 DRAM ( J7J1, J7J2)

12 Yamaha wavetable module

1 Sec Pri

J7C1 J9A1

3

1

J6F1 Hard disk

Fan 1 Yamaha wavetable module

1 12 2

LED (HDD LED)

J8H3

34

J7D1

1 5

Floppy

33

20 J8H1 J8H2

2 1

PCI IDE(2)

39

J10H1

1

8 GP I/O

J9D1

27

1 Front panel I/O connectors


Connector pinouts of an Intel PD440FX motherboard.

Intel

Corporation

to-analog converters; analog mixing, anti-aliasing, and reconstruction filters for sound re production; line, microphone, and monaural inputs; ADPCM, AD PCM, A-law, or M-law digital audio compression and decompression; full digital control of all mixer and volume-control functions; software switching between rear-panel mic-in and line-in connectors; Plug-andPlay compatibility; and Sound Blaster Pro and Windows Sound System compatibility. 4 CD-ROM audio connector This is necessary to play CD audio through the mother board’s sound system (used in conjunction conjunction with on-board sound). It is a 4-pin header and the pinout is shown in Table 28-1. 5 Telephony connector Telephony support is available on some motherboards for connecting the monaural audio signals of an “internal telephony device” to the motherboard’s audio subsystem. A monaural audio-in and audio-out audio-out signal interface interface is necessary for


946 94 6

MOTH MO THER ERBO BOAR ARD D TROUB TROUBLE LESH SHOO OOTI TING NG

T AB AB LE LE 2 88- 1 C DD- RO RO M A UD UD IO IO CONNECTOR PINOUT

P IN

SIGNAL NAME

1

Ground

2

CD L e f t

3

Ground

4

CD Right

T AB AB LE LE 2 88- 2 T EL EL EP EP HO HO NY NY CONNECTOR PINOUTS 1X4 ATAPI CONNECTOR

P IN

SIGNAL NAME

1

MONO IN (from external device)

2

Ground

3

Ground

4

MONO OUT (to external device)

2X2 CONNECTOR

P IN

SIGNAL NAME

1

Ground

2

MONO IN (from external device)

3

MONO OUT (to external device)

4

Key

telephony applications, such as speakerphones, fax/modems, and answering machines. Two different interface headers are available for this application: a general telephony interface with a 1- × 4-pin ATAPI-type connector (Table 28-2), and a telephony interface with a 2- × 2-pin header (same function as #7). 6 Wavetable header This 2- × 4-pin header supports wavetable wavetable add-in cards. Most wavetable add-in cards are installed in an ISA slot, and a cable is routed from the card to this header. Compatible wavetable cards include the ICS WaveFront WaveFront and the CrystaLake Series 2000 wavetable product. 8 Line-in connector The line-in connector is available for connecting left and right channel signals of an internal audio device device to the motherboard’s audio subsystem. subsystem. An audio-in signal interface of this type is necessary for such applications as TV tuner boards. A general audio interface is provided with a 1- × 4-pin ATAPI-type connector (Table 28-4). 9 Back-panel I/O connectors These are the group of I/O connectors that reside on the back panel. These include serial ports, parallel ports, ports, USB ports, keyboard and mouse


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10 ports, game/MIDI ports, and sound connections. connections. Figure 28-7 illustrates illustrates a typical ATX

back panel. 10 Slot-1 processor connector The processor connects to the motherboard through the

Slot-1 processor connector, a 242-pin edge connector. connector. When the processor is mounted in Slot 1, it is secured secured by a “retention mechanism” mechanism” attached to the motherboard. motherboard. The processor’s heatsink is stabilized by a heatsink support that is attached to the mother board. 11 Intel SB82442FX Data Bus Xccelerator (DBX) This is part of 440FX chipset, which controls the memory operations of the motherboard. The DBX connects to 64-bit processor data bus, the 64- or 72-bit memory data bus, and the 16-bit PMC chip’s private-data bus. The DBX works in parallel with the PMC chip to provide a high-performance memory subsystem. 12 Intel SB82441FX PCI Bridge and Memory Controller (PMC) This is part of 440FX chipset. The PMC chip provides bus-control signals and and address paths for


TABLE TABL E 28-3 WAV WAVETAB ETABLE LE CON CONNEC NECTOR TOR PINO PINOUT UT

P IN

SIGNAL NAME

P IN

SIGNAL NAME

1

Wave In Right

2

Ground

3

Wave In Left

4

Ground

5

Key

6

Ground

7

Not connected

8

MIDI Out (from host)

T AB AB L E 2 8 - 4 L I NE NE I N CONNECTOR PINOUT

P IN

SIGNAL NAME

1

Left Li ne In

2

Ground

3

Ground

4

Right Line In (monaural)

Keyboard

Parallel port

MIDI/game port

USB 1

Mouse USB 0


Serial port 1

Serial port 2

2

Line out

Connector layout of a typical ATX back panel.

Mic in Line in

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data transfers tran sfers between the host bus, PCI bus, and and main memory. The 82441FX provides the following features: s Microprocessor interface control, including processor host bus speeds up to 66 MHz and 32-bit addressing. s An integrated DRAM controller providing a 64- or 72-bit non-interleaved path to memory with ECC support, support for EDO DRAM, and support for 8MB to 256MB of main memory. s A fully synchronous PCI bus interface that is compliant with the PCI specification revision 2.1 and operating at 33MHz PCI-bus speed for PCI-to-DRAM speed greater than 100MB/sec. 13 Power connector This is a 20-pin PS/2-type power connector that supplies +5, -5, +12, -12, and +3.3 V to the ATX motherboard. Table 28-5 lists the pinout pinout for this power connector. 14 Speaker This is a small small integrated general-purpose general-purpose speaker. speaker. Some motherboards might replace an integrated speaker with a 2-pin header for an external speaker in the case. 15 Battery The CMOS RAM backup battery. 16 SIMM sockets The sockets for 72-pin SIMMs—later motherboards use 168-pin DIMMs. 17 IDE connectors The 40-pin primary and secondary drive-controller channels for ATA (IDE), ATA-2 (EIDE), and ATAPI devices (such as CD-ROM drives). 18 GP I/O header A general-purpose I/O connector. Table 28-6 lists the pinout for a GP I/O connector. 19 Floppy-drive connector The 28-pin floppy-drive channel. 20 Intel SB82371SB PCI/ISA IDE Xccelerator (PIIX3) 21 Front-panel header The group of connectors used to connect front-panel switches and indicators, such as the speaker, reset switch, power LED, hard-drive activity LED (HDD LED—same as #20), infrared (IrDA) (IrDA) port, sleep switch, or power switch. switch. Figure 28-8 shows a typical header header arrangement for an ATX motherboard. motherboard. Table 28-7 lists the pinout the header connectors. 22 TSOP flash device The BIOS ROM IC. TABLE TAB LE 28 28-5 -5 ATX POWE POWER R CONNEC CONNECTO TOR R PINOUT PINOUT

CONNECTOR

SIGNAL NAME

CONNECTOR

SIGNAL NAME

1

+ 3.3 V

11

+ 3.3 V

2

+ 3.3 V

12

–12 V

3

Ground

13

Ground

4

+5 V

14

PW_ON#

5

Ground

15

Ground

6

+5 V

16

Ground

7

Ground

17

Ground

8

PWRGD (power good)

18

–5 V

9

+5 VSB (standby for real-time clock)

19

+5 V

+12 V

20

+5 V

10


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T AB AB L E 2 8 - 6 G P I/ I/ O CONNECTOR PINOUT

P IN

SIGNAL NAME

1

Vcc

2

Key

3

GP1 7

4

Ground

5

GP1 2

6

Ground

7

GP1 1

8

Ground

Speaker

Reset

Pwr LED

HD LED

Infrared

2

Sleep Pwr on

27

1

FIGU FIGURE RE 28-8 28-8

Front-panel header layout for a typical ATX motherboard.

TABLE TAB LE 28 28-7 -7 FRON FRONT T PAN PANEL EL HE HEAD ADER ER ASSIGNMENTS

P IN

SIGNAL NAME

1

SW_ON#

2

Ground

3

SLEEP

4

Sleep Pullup (SLEEP_PU)

5

No connect

6

+5 V

7

Key

8

IrRX

9

Ground

10

IrTX

11

Consumer IR (CONIR)

12

No connect

13

HD_PWR +5 V

14

Key

15

HD Active#

16

HD_PWR

17

No connect

18

Ground

19

Key

20

PWR_LED

21

No connect

(power-on connector) (sleep/resume switch)

(IrDA connector)

(HDD LED connector)

(sleep/power LED)


950 950


TABLE TAB LE 28 28-7 -7 FRON FRONT T PAN PANEL EL HE HEAD ADER ER ASSIGNMENTS (CONTINUED)

P IN

SIGNAL NAME

22

Ground

23

SW_RST

24

Ground

25

Key

26

PIEZO_IN

27

SPKR_HDR

(Reset switch) (Speaker)

23 Configuration jumper block The group of jumpers used to configure the motherboard.

Typical configuration jumpers can include (but are not limited to): s Bus speed One or more jumpers used to set the motherboard bus speed. s Clock multiplier One or more jumpers used to multiply the bus speed for the given CPU. s CPU type One or more jumpers used to define the presence of an Intel, AMD, or Cyrix CPU. s CPU voltage(s) One or more jumpers used to select the particular operating voltage(s) for a given CPU. s Video port If the motherboard offers on-board video, this jumper enables or disables it. s Hard drives If the motherboard offers on-board hard-drive ports, this jumper enables or disables it. s Floppy drives If the motherboard offers an on-board floppy-drive port, this jumper enables or disables it. s CMOS clear This jumper can be used to clear the CMOS (NVRAM and ESCD). s Clear password This jumper can be used to erase the CMOS password(s) without clearing the CMOS. s CMOS access This jumper can be used to prevent access to the CMOS setup routine. s BIOS recovery This jumper can be used to invoke BIOS boot block recovery if a BIOS flash upgrade fails. 24 National PC87307VUL I/O controller The PC87307 super I/O controller from National Semiconductor is an ISA Plug-and-Play compatible, multifunction I/O device that provides the following features: s Two serial ports Including two 16450/16550A-software compatible UARTs, an internal send/receive 16-byte FIFO buffer, and four internal 8-bit DMA options for the UART with SIR support (USI). s A multimode bi-directional parallel port that can operate in Standard mode (IBM and Centronics compatible), Enhanced Parallel Port (EPP) mode with BIOS and driver support, or high-speed Extended Capabilities Port (ECP) mode. s A floppy-disk controller that is DP8473 and N82077 compatible. s A keyboard and mouse controller that is industry-standard 8042A compatible. s A real-time clock that is DS1287 and MC146818 compatible, and is accurate within ±13 minutes/year at 25°C with 5 V applied.

TROUBLESHO TROUBLESHOOTIN OTING G A MOTHERBOAR MOTHERBOARD D

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TABLE TAB LE 28 28-8 -8 YAMA YAMAHA HA WAVE WAVETAB TABLE LE MODULE MODULE CONNECTOR PINOUTS

P IN

SIGNAL NAME

P IN

SIGNAL NAME

1

EXTEN#

1

RSTDRV

2

S IN

2

VCC

3

VCC

3

AUD33MHZ

4

Ground

4

MIDI Out

5

BCK

5

Ground

6

LACK

6

Key

Support for Advanced Power Control (APC). s Support for an IrDA and consumer IR-compliant infrared interface. 25 Fan 1 header A connector used to power a fan in the system and detect its operation (same function as #30). Pin 1 is ground, pin 2 is +12 V, and pin 3 is a “fan sense” line, which can be monitored m onitored by the management-extension hardware (#29). 26 Yamaha wavetable module headers Two optional 2- × 3-pin connections are used for Yamaha wavetable cards (Table 28-8). These connectors are not identical, and the one you use will depend on the particular wavetable card installed. 27 Chassis security header A “tamper” switch contact used in conjunction with management-extension hardware (#29). 28 Management-extension hardware This optional management-extension hardware provides low-cost instrumentation capabilities that are designed to reduce the total cost of owning a PC. The hardware implementation is a single-chip ASIC, which inincludes such features as: an integrated temperature sensor, fan speed sensors for up to three fans, power-supply voltage monitoring to detect levels above or below acceptable values, and a header for an external chassis-security switch feature. 29 PCI connectors For PCI adapter boards. s

Troubleshooting a Motherboard Because motherboards contain the majority of system processing components, it is likely that you will encounter a faulty faulty motherboard sooner or later. later. The BIOS POST is written to test each sub-section of the motherboard each time the PC is powered up, so most problems are detected well before before you ever see the DOS prompt. Errors are reported in a myriad of ways. Beep codes and POST codes (Chapter 19) provide indications indications of fatal errors errors that occur before the video system is initialized. initialized. Still, plenty of symptoms can elude the initial testing at start start time. This part of the chapter digs in and presents presents a lengthy selection of motherboard symptoms for you to reference.

REPAIR VS. REPLACE This is the perennial troubleshooting dilemma. The problem with motherboard repair is not so much the availability of replacement parts (although that can be a challenge) as is

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952 952


the use of surface-mount soldering (SMT). You see, a surface-mounted surface-mounted IC cannot cannot be desoldered with conventional tools. tools. To successfully desolder a surface-mounted surface-mounted IC, you need to heat each of the IC’s pins (often in excess of 100) simultaneously, then lift the IC off the board. board. It is then then a simple matter to clean clean up any residual solder. solder. Unfortunately, specialized surface-mount surface-mount soldering equipment is required to do this. this. The equipment is readily available commercially, so it is easy to buy—but you can invest $1000 to $2000 to equip your work bench properly. As you can imagine, the “repair vs. replace” decision decision is an economic one. It makes little sense for the part-time PC enthusiast to make such a substantial investment to exchange a defective IC (which are usually under $30). It is generally better to replace the mother board outright, which is only a fraction of the cost of such SMT equipment. equipment. On the other hand, professionals who intend to pursue PC repair as a living are well served with surface-mount equipment. The customer’s cost for labor, the part(s), and markup is typically much less than purchasing a new motherboard (especially the high-end boards such as i486/66 and Pentium motherboards).

START WITH THE BASICS Because motherboard troubleshooting represents a significant expense, be sure to start any motherboard repair by inspecting inspecting the following points in the PC. Remember to turn all power off before performing these inspections: Check all connectors This can happen easily when the PC is serviced or upgraded, and you accidentally forget to replace every cable (or the cable is installed incorrectly). Start with the power connector, and inspect each cable and connector attached to the motherboard. Frayed cables should be replaced. Loose or detached cables cables should be reattached properly. s Check all socket-mounted ICs Some ICs in the computer (especially the CPU) get hot during normal operation. It is not unheard of for the repetitive expansion and contraccontraction encountered with with everyday use to eventually eventually “rock” an IC out of its socket. The CPU, math-co-processor (on older motherboards), BIOS ROM, and often the CMOS/ RTC module are socket mounted, so check them carefully. Check power levels Low or erratic ac power power levels can cause cause problems in the the PC. Use s a multimeter and check ac at the wall outlet. Be very careful whenever dealing with ac. Take all precautions to protect yourself from injury. If the ac is low or is heavily loaded by motors, coffee pots, or other highly inductive loads, try the PC in another outlet running from a different circuit. If ac checks properly, use your multimeter (or a measurement tool, such as PC Power Check from Data Depot) to check the power supply outputs. If one or more outputs is low or absent, you should repair or replace the supply. s Check the motherboard for foreign objects A screw, paper clip, or free strand of wire can cause a short circuit that that might disable the motherboard. motherboard. Examine the motherboard carefully and use ample lighting. s Check that all motherboard DIP switches and jumpers are correct For example, if the motherboard provides a video port and you have a video board plugged into the expansion bus, the motherboard’s video circuit will have to be disabled through a switch or jumper. Otherwise, a hardware conflict conflict can result that that might interfere with mothers

TROUBLESHOO TROUBLESHOOTING TING A MOTHERBOAR MOTHERBOARD D

953

board operation. You will need the user manual for the PC to identify identify and check each jumper or switch. s Check for intermittent connections and accidental grounding Inspect each of the motherboard’s mounting screws, and see that they are not touching nearby printed traces. Also check the space under the motherboard and see that nothing that is grounding the mother board and chassis. As an experiment, you might try loosening the motherboard mounting screws. If the fault goes away, the motherboard might be suffering from an intermittent connection—when all screws are tight, the board is bent just enough to let the intermittent appear. Unfortunately, intermittent connections are almost impossible to find.

SYMPTOMS Symptom 28-1. A motherboard failure is reported, but goes away when the PC’s outer cover is removed An intermittent connection is on the motherboard.

When the housing is secured, the PC chassis warps just slightly—this might be enough to precipitate an intermittent contact. When the housing is removed, the chassis relaxes and hides the intermittent connection. Replace the outer cover and gently re-tighten each screw with the system running. Chances are that you will find one screw that triggers the problem. You can leave that screw out, but it is advisable to replace the motherboard as a long-term fix. Symptom 28-2. The POST (or your software diagnostic) reports a CPU fault This is a fatal error, error, and chances are that system system initialization has halted. CPU

problems are generally reported when one or more CPU registers do not respond as ex pected, or has trouble switching switching to the protected protected mode. In either case, the CPU is probaproba bly at fault. Fortunately, the CPU is socket socket mounted and should be very straightforward straightforward to replace. Be sure to remove all power to the PC and make careful use use of static controls when replacing a CPU. Mark the questionable questionable CPU with indelible ink before replacing replacing it. Zero-Insertion Force (ZIF) sockets are easiest because the IC will be released simply by lifting the metal lever lever at the socket’s side. Slide out the original CPU and insert a new new one. Secure the metal lever lever and try the PC again. However, many CPUs are mounted in PinGrid Array (PGA) sockets, and a specialized PGA-removal tool is strongly suggested for proper removal. You should also be able to use a small, regular screwdriver screwdriver to gently pry up each of the four sides of the CPU, but be very careful to avoid cracking the IC, the socket, or the motherboard—never motherboard—never use excessive force. force. If the IC is free, install install the new CPU with close attention to pin alignment, then gently press the new CPU into place. A word about heatsink/fans. heatsink/fans. Most i486 (and later) later) CPUs are equipped with a metal metal heatsink (or heatsink/fan) heatsink/fan) assembly. It is vital to the proper operation operation of your system that the heatsink be re-installed re-installed correctly. Otherwise, the new CPU will eventually overheat overheat and lock up or fail. Be sure to use good-quality thermal compound to ensure proper proper heat transfer to the heatsink (remember that a sound mechanical connection does not guarantee a good thermal connection). Symptom 28-3. The POST (or your software diagnostic) reports a problem with the floating-point unit Math co-processor (also called the Floating-Point Unit,

FPU ) problems are generally reported when one or more MPC registers do not respond as expected. Fortunately, MCP faults faults are not always fatal. It is often possible to remove remove the

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MCP or disable the MCP availability availability through the CMOS setup. Of course, programs that depend on the MCP will no longer run, but at least the system can be used until a new one is installed. On older systems that use separate separate MCPs, the device is socket mounted, and should be very straightforward straightforward to replace. replace. Be sure to remove all power to the PC, and make careful use of static static controls when replacing replacing an MPC. Mark the questionable questionable MPC with indelible ink before replacing replacing it. If the MCP is integrated into the CPU (i386DX, (i386DX, i486DX, Pentium, and later CPUs) are a bit more expensive because you’ll need to replace the entire CPU, but the replacement process is no more difficult (remember to remount any heatsink/fan assembly properly). Symptom 28-4. The POST (or your software diagnostic) reports a BIOS ROM checksum error The integrity of your system BIOS ROM is verified after the

CPU is tested. This is necessary to ensure that no unwanted instructions or data could easily crash the system during POST or normal normal operation. A checksum is performed on the ROM contents, and that value is compared compared with the value stored in the the ROM itself. If the two values are equal, the ROM is considered good and initialization continues. Otherwise, the BIOS is considered defective and should be replaced. Chapter 6 provides an index of major BIOS manufacturers. Traditionally, BIOS ROM is implemented as one or two ICs that are plugged into DIP sockets. They can be removed easily with the blade of a regular screwdriver, screwdriver, as long as you pry the IC up slowly and gently (be (be sure to pry the IC evenly from from both ends). When installing new DIP ICs, you might have to straighten their pins against the surface of a table or use a DIP pin-straightening tool. Ultimately, the IC pins will fit nicely into each receptacle in the the DIP socket. You can then ease the IC evenly into the the socket. Alignment is crucial to ensure that all all pins are inserted. If not, one or more pins might be bent under the IC and ruin the new ROM. Also, be sure to insert the new IC(s) IC(s) in the proper orientation. If they are accidentally installed installed backward, they might be damaged. Newer BIOS ICs use flash EEPROM technology, which allows the device to be erased and reprogrammed in the field without without having to replace the entire entire BIOS ROM IC. When a flash BIOS fails its checksum test, test, it also has probably failed. Because flash BIOS devices are often fabricated as PLCC ICs, it is a bit easier to replace them, but you will need a PLCC-removal tool to take the original IC out of its socket—there simply is not enough room for a screwdriver. Symptom 28-5. The POST (or software diagnostic) reports a timer (PIT) failure, an RTC update problem, or a refresh failure The PIT is often an 8254

or compatible device. Ultimately, one or more of its three channels might have have failed and the PIT should be replaced. It is important to realize that many modern motherboards inincorporate the PIT functions into a system controller or other chipset IC (refer to Chapter 8 for a listing of chipsets and and functions). Because the PIT is typically surface surface mounted, you can attempt to replace the device or replace the motherboard entirely. Symptom 28-6. The POST (or software diagnostic) reports an interrupt controller (PIC) failure The PIC is often an 8259 or compatible device, and two PICs are on

the typical AT motherboard (PIC#1 handles IRQ0 through IRQ7, and PIC#2 handles IRQ8 through IRQ15). Of the two, PIC#1 is more important because the lower interrupts have a higher priority, and the lowest channels handle crucial low-level functions, such as the sys-


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tem timer and keyboard interface. Generally, a diagnostic will reveal which of the two PICs have failed. Be sure that no interrupt conflicts are between two or more system devices. You can then replace the defective PIC. In many current systems, both PICs are integrated into a system controller or chipset IC. You can replace the defective IC if you have the ap propriate surface-mount equipment available, or replace the motherboard entirely. Symptom 28-7. The POST (or software diagnostic) reports a DMA controller (DMAC) failure The DMAC is often an 8237 or compatible device, and two

DMACs are on the typical AT motherboard (DMAC#1 handles channel 0 through channel 3 and DMAC#2 handles channel 4 through channel channel 7). Of the two, DMAC#1 is more im portant because channel 2 runs the the floppy-disk controller. Generally, a diagnostic will reveal which of the two DMACs have failed. Be sure that no DMA conflicts conflicts are between two or more system devices. You can then replace the defective defective DMAC. In many current systems, both DMACs are integrated into a system system controller or chipset IC. You can re place the defective IC if you have the appropriate surface-mount equipment available, or replace the motherboard entirely. Symptom 28-8. The POST (or software diagnostic) rep orts a KBC fault The

KeyBoard controller (KBC) is often either an 8042 or an 8742. Because the KBC is a microcontroller in its own right, diagnostics can usually detect a KBC fault with great accuracy. The KBC might either either be a socket-mounted socket-mounted PLCC device, or (in rare cases) a surface-mounted IC. Remember, remove all power and mark the old KBC before you remove it from the PC. You will probably need a PLCC-removal tool tool to take out the old KBC. If you cannot exchange a defective KBC, you’ll need need to replace the motherboard. Symptom 28-9. A keyboard error is reported, but a new keyboard has no effect The keyboard fuse on the motherboard motherboard might have failed. Many motherboard de-

signs incorporate a small fuse (called a pico-fuse) in the +5-Vdc line that drives the key board. If this fuse fails, the keyboard keyboard will be dead. dead. Use your multimeter and measure the +5-Vdc line at the keyboard connector. connector. If this reads 0 Vdc, locate the keyboard keyboard fuse on the motherboard and replace it (you might have to trace the line back to the fuse, which looks almost exactly like a resistor). Symptom 28-10. The POST (or software diagnostic) reports a CMOS or RTC fault With either error, the same device is usually at fault. The CMOS RAM and RTC

are generally fabricated fabricated onto the sane device. RTC problems indicate that the real-time real-time clock portion of the IC has failed or is not being updated. CMOS RAM failure can be caused by a dead backup battery or by the the failure of the IC itself. itself. When dealing with a CMOS or setup problem, try the following protocol. First, try a new backup battery battery and reload the CMOS setup variables. If a new battery does not resolve the problem, problem, the CMOS/RTC IC should be replaced. Often, the CMOS/RTC IC is surface mounted, and will have to be replaced (or the motherboard will have to be replaced). replaced). However, the growing trend is toward making the IC socket mounted and including the battery into a single replaceable module (such as the Dallas Semiconductor-type devices). devices). Modules are typically replaceable replaceable DIP devices. Symptom 28-11. The POST (or software diagnostic) reports a fault in the first 64KB of RAM The first RAM page is important because it holds the BIOS Data

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vectors—the system will not work without it. it. When a RAM er Area (BDA) and interrupt vectors—the ror is indicated, your only only real recourse is to replace the motherboard RAM. On older motherboards, if the diagnostic indicates which bit has failed and you can correlate the bit to a specific IC, you can sometimes replace the defective IC (typically, surface mounted). Otherwise, you will need to locate and replace all of the motherboard RAM, or replace the motherboard entirely. entirely. Newer motherboards utilize utilize SIMMs or DIMMs for all system memory, so it should be relatively simple to cycle through each SIMM or DIMM with a known-good unit and isolate the defective memory. Symptom 28-12. The MCP does not work properly when installed on a motherboard when external caching is enabled Some non-Intel math co-

processors or FPUs work in areas that that must be non-cached. For example, a Cyrix EMC87 MCP with an AMI Mark IV i386 motherboard has been known to cause these types of problems. When MCP problems arise (especially (especially during upgrades), try try disabling the external cache through CMOS setup. As another alternative, try a different math co-processor. Symptom 28-13. A “jumperless motherboard” receives incorrect CPU Soft Menu settings and now refuses to boot This might occur on a motherboard, such

as the Abit IT5V, and is usually caused by accidental settings during system configuration. Fortunately, this type of problem can be corrected by removing power from the mother board—try turning off the the system and unplugging it for several minutes. When you restore power to the system, the CPU soft menu will automatically reset the CPU frequency for the lowest setting setting and allow the motherboard to to boot. You can then go back into the CPU soft menu and correct any speed-setting errors. errors. If this were a jumpered motherboard, you would need to find the CPU speed jumper and set it correctly. Symptom 28-14. 28-14. When installing two 64MB SIMMS, SIMMS, only 32MB of RAM are displayed when the computer is turned on The motherboard is probably using a

430VX chipset that (although supporting 128MB of RAM) will not support 64MB memory devices. The 430VX only supports the following memory devices: devices: s s s s

512K × 32 bit (2MB) 1M × 32 bit (4MB) 2M × 32 bit (8MB) 4M × 32 bit (16MB)

The layout for a 64MB SIMM is 16M × 32 bit, which isn’t isn’t in the preceding preceding list. When you install two 64MB SIMMs, the system will use the 4M- × 32-bit specification to calculate the memory, thus displaying displaying 32MB. Unfortunately, this limitation limitation of the mothermother board cannot be corrected without upgrading the motherboard. Symptom 28-15. A Creative Labs PnP sound board refuses to work on one motherboard, but the board works just fine on another motherboar d In this

issue, the PnP BIOS is usually usually at fault. Check with the motherboard motherboard manufacturer to see if a BIOS update is available to correct PnP problems.

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Symptom 28-16. The system CD-ROM drive refuses to work once an IDE bus master driver is installed This is almost always a driver problem, which is not

interacting properly properly with the IDE/EIDE bus controller controller on the motherboard. In almost all cases, you should update the IDE bus master driver or disable bus mastering completely. Symptom 28-17. You cannot get an AMD 5x86 133MHz CPU to run on your motherboard Check your voltage first. The AMD 5x86 runs on 3.3 V, so you might need

a voltage regulator in the CPU socket (the AMD CPU might already be damaged). Also check your BIOS version—you might need an updated BIOS to support the AMD CPU properly. Check your jumper settings next—the speed or CPU type selection is almost always always set wrong. If you cannot jumper the motherboard motherboard correctly (i.e., 33MHz bus speed), speed), then the motherboard itself is limited—it cannot enable the 4 × internal CPU clock for the AMD 5x86. In this case, you will need to use a different CPU or replace the motherboard outright. Symptom 28-18. You cannot get a Cyrix 5x86 CPU to run on your motherboard Check your voltage first. The Cyrix 5x86 uses 3.3 V, so you might need a volt-

age regulator in the CPU socket socket (the Cyrix CPU might already be damaged). damaged). Also check your BIOS version—you might need an updated BIOS to support the Cyrix CPU properly. Check your jumper settings next—the speed (33MHz) or CPU-type selection is almost always set wrong. If problems persist, you might need a different different CPU or motherboard. Symptom 28-19. You see the error message “System Resource Conflict” on the AMI BIOS POST display This error is generated by AMI PnP BIOS (although

other PnP BIOS might produce similar errors) when the BIOS detects a resource conflict during initialization. initialization. You might try to force the BIOS to reconfigure the conflicting resource by pressing the key during POST. If problems continue, you might need a BIOS update, which might be able to resolve assignment conflicts more intelligently. Otherwise, you might need to try to reconfigure the conflicting resource manually (disabling its PnP support), or remove the offending device entirely. Symptom 28-20. The system hangs after using MEMMAKER under DOS

This is most prevalent with AMI’s A MI’s WinBIOS, which cannot support the “highscan” option used with EMM386.EXE. Be sure to disable the “highscan” “highscan” option from EMM386 before running MEMMAKER. You might also choose to upgrade the system system BIOS to a more recent version, which might be more robust when testing memory. Symptom 28-21. The Power management icon management icon does not appear in the Windows 95 Control panel This occurs even though the APM parameter under the BIOS

power-management setup is enabled. enabled. This problem occurs if you do not enable the APM function before you install install Windows 95. If you have already installed Windows Windows 95, you must re-install it. Before doing so, however, be sure that the APM function function is enabled. Symptom 28-22. Systems with a Western Digital 1.6GB HDD fail to boot even though BIOS recognized the presence of HDD This is a typical problem

with large hard drives, which often need additional time to start up after powering the system. Check your BIOS advanced setup and increase the the “Power-on Delay” time. time. This

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should correct the problem. problem. This problem might reoccur if if CMOS default values are rereloaded or if CMOS contents are lost. Symptom 28-23. After installing Windows 95, the system can no longer find the CD-ROM drive on the secondary IDE channel You might also find that

the IDE drives are running in MS-DOS “compatibility mode.” This problem occurs often with motherboards using the Intel 430HX chipset—Windows 95 is not recognizing the Intel 82371SB drive controller on the motherboard, which causes BIOS to disable the secondary IDE channel—devices on the secondary channel are not being detected after the system is rebooted. In most cases, you can upgrade the BIOS to correct this problem or move the IDE devices to a separate IDE controller. You might also be able to find an update to the MSHDC.INF file, which will force Windows 95 to recognize the 82371SB controller. Symptom 28-24. The system hangs up or crashes when the chipset-specific PCI-IDE DOS driver is loaded This is a known problem with Micro-Star moth-

erboards using a VIA VP1 chipset and Award BIOS 4.50PG. The problem is with with the BIOS version and its interaction interaction with the PCI controller portion of the VIA chipset. Upgrading the BIOS version should resolve the problem. Symptom 28-25. The Pentium motherboard is unusually picky about which SIMMs it will accept This occurs even though the SIMMs are all within the

proper type and rating. Consider several possible problems. First, Intel chipsets chipsets are very discriminating when it comes to memory speed, so be sure that the memory speed is well within the required range (usually (usually 70 ns or faster). Second, try changing the wait states in the CMOS setup to a lower speed (e.g., 4-4-4-4). 4-4-4-4). If your system works under this low speed, then increase the speed (e.g., 3-3-3-3, 3-2-2-2, 3-1-1-1, etc.) and keep trying until the best number has reached. reached. Finally, the memory itself might be of questionable qualquality—try good-quality memory, memory, bought from a reputable vendor. Be sure that the vendor offers a liberal return policy so that you can return questionable memory easily. Symptom 28-26. You experience a problem with pipeline burst cache This

is a recognized problem with UMC pipeline burst cache (especially on an Amptron motherboard). The problem can usually be solved by adjusting adjusting the cache control to 4-4-4-4 4-4-4-4 (the default in CMOS is typically typically 2-3-3-3). This will reduce performance, performance, but it should stabilize cache operations. Symptom 28-27. You get no display, or the system refuses to boot because of the keyboard controller Notice that the video adapter proves out fine in

another system. This is a problem with the VIA 82C41 24-pin 24-pin keyboard controller (espe(especially on the Amptron PM-7600 PM-7600 motherboard). A fault with the KBC might cause cause a “no display” or “fail to boot” boot” condition. The VIA 82C41 is extremely sensitive to to damage from power-supply surges/spikes, surges/spikes, and ESD damage. Replace the KBC or replace replace the motherboard with a more robust model. Symptom 28-28. Your customer forgets their password The PC password is

stored in the CMOS RAM, RA M, which is located in either the motherboard chipset or the real-


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time clock chip. If it is stored in the chipset, the CMOS memory is backed up by a coinshaped lithium battery battery (or other battery). If it is stored in the the RTC chip, it has an internal battery to back up the CMOS RAM. For the external external battery, follow these steps: First, make a complete backup of the CMOS settings. Turn off the system, and remove remove the battery for at least two hours. This should clear the CMOS setting and erase the the password. For the RTC battery, follow follow these steps: Determine which RTC chip you have—the have—the five different kinds of real-time clock CMOS chips are: s s s s s

Dallas DS 12887 real time Benchmarc Dallas DS 12B887 Dallas DS 12887A BQ3287A

For the Dallas DS 12887 and Benchmarc RTC chips, if you can boot to the A: prompt, flash the BIOS chip with the same boot block record, but different BIOS revision. For example, if you have a P/I P55TP4XE motherboard with BIOS revision 0202, flash the BIOS chip to BIOS revision 0115. A BIOS checksum error error will be generated. Enter the CMOS setup screen, reload setup defaults, then save and exit. At this point, the password has been cleared. You can flash the BIOS back to the original revision. If you can’t boot to the A: prompt, turn off the system, remove the BIOS chip, and insert another with the same boot block record but different BIOS revision. Power on the system. A BIOS checksum error will be generated. Turn off the system. Reinstall the original BIOS. Power on the system again, and hit to enter the BIOS setup screen. Reload the setup defaults, then save and exit. For the Dallas DS 12887A, a jumper is on the motherboard, which clears the CMOS. Please check your manual for the location of this jumper (it will vary between mother boards). Shorting this jumper should erase erase the system-configuration system-configuration information (including password) stored in the the CMOS. To clear the CMOS, be sure that the system system is off. Short the jumper for a moment and then then remove it. Do not leave this jumper shorted. After clearing the CMOS, the password should be erased. For the BQ3287A and Dallas DS12B887 RTC chips, short the same jumper (as in the previous section), but be sure to power the system on and off before removing the jumper. Symptom 28-29. You encounter problems with Western Digital hard drives (the drives work on other systems) This type of problem has been identified

with Asus motherboards using Award BIOS with older Western Digital (~1.6GB) drives. Notice that problems do not not appear in newer Western Western Digital drives. There are several means of addressing the problems: First, disable the “Quick Power-on Power-on Self Test” in your CMOS setup, and enable the “floppy “floppy seek” option. This will increase the time time that the drive gets to spinup. If your CMOS offers a “Power-on Delay Delay Time” instead, try increasing that time. Also avoid using DEFRAG, or the “disk surface scan” feature feature of ScanDisk with Western Digital drives—both have been reported to increase the number of bad blocks on the disk. Next, consider a BIOS upgrade (especially if you’re using a motherboard with the Intel 430FX chipset). Some BIOS versions use a “park head” head” command that can cause probproblems with Western Western Digital hard drives. drives. Finally, check the Western Western Digital Web Web site

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(http://www.wdc.com) for any drive patches that that might be currently available. available. If all else fails, you can replace the drive outright. Symptom 28-30. You encounter memory parity errors at bootup If you’re us-

ing non-parity memory devices (e.g., a 32-bit device instead of a 36-bit device), you will need to disable DRAM ECC or parity checking through the CMOS chipset features settings. This problem can occur if you reload default CMOS settings, which restores parity/ECC on a system with non-parity memory. Also, the Triton chipset does not support parity, so even if you use parity RAM, you should try disabling parity checking. If the system is configured properly, you might actually have a memory failure, and you’ll need to isolate the memory fault. Symptom 28-31. You flash a BIOS, but now you get no video When you flash

a BIOS, the CMOS settings are left useless. This means you will have to restore the proper proper CMOS settings before before the system might run run properly. Clear your CMOS and reload the proper settings. The BIOS IC itself itself might also also be troublesome. troublesome. There are some problems when flashing an Intel flash ROM IC. Be sure that no warnings or cautions are in the system documentation or from the manufacturer’s manufacturer’s Web site before flashing a particular particular BIOS IC. Try restoring the original BIOS, if possible, or contact the manufacturer for a replacement BIOS. Symptom 28-32. You are trying to use a PnP sound card and PnP modem together on the same system, but you’re getting hardware conflicts This

is an all-too-common all-too-common problem with PnP systems. In general, the modem should should take COM2 (2F8h and IRQ3), and the sound card should should take 220h, IRQ5, and DMA 1. Try adding the cards one at a time—install the sound card first and let Windows 95 detect it. Add the modem next. If problems persist, configure the cards cards manually (disable their PnP support), if possible. Symptom 28-33. After setting the DRAM speed to 70 ns in the Advanced chipset setup, the system crashes or refuses to boot Chances are that you

have the incorrect number of wait states set for your memory configuration—70-ns RAM typically requires at least one wait state. Disable any “Auto configure DRAM timing” feature, then set the number of wait states states to 1. That should clear up the problem. Symptom 28-34. 32MB (or more) of memory is installed, and the BIOS counts it all during POST, but you only see 16MB in the CMOS setup screen

This problem has been identified with some Award BIOS versions. To correct the problem, be sure that the “memory hole” option in the Advanced chipset setup area is disabled. The “memory hole” option assumes assum es that a maximum of 16MB of physical RAM RA M is in the system. Symptom 28-35. You move a working IDE drive from an older 386/486 system to your new Pentium system, but the system no longer works In most

cases, the data-transfer mode is set improperly for the old IDE hard drive (e.g., using LBA mode when the IDE drive requires CHS mode). Find the Peripheral setup screen in your CMOS setup and be sure to change all the PIO mode settings to Mode 0 (chances are the settings are currently at Automatic, and are configuring configuring the data transfer incorrectly). incorrectly). In some cases, you might need to repartition and reformat the drive to use it on a different (older) controller.


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Symptom 28-36. Windows 95 locks up when you install a Diam ond Stealth Video 3200 board and an Intel EtherExpress Pro 10/100 network card

However, you verify that both both cards work fine on other systems. systems. Problems begin when you load the Intel network driver. driver. This is a problem that has been identified identified with Premio motherboards and is caused by a problem problem in the system BIOS. Upgrade the Premio BIOS to the latest version. Symptom 28-37. You install an Intel Pentium P55C (MMX) 200MHz CPU, and you set the CPU speed jumper(s) for 200MHz, but the system still reports 166MHz In virtually all cases, you have set the speed speed jumper(s) incorrectly. Take

another look at the documentation for your motherboard and see that the speed is indeed set correctly. If problems persist, the BIOS might not recognize the higher CPU speed correctly, so try upgrading the motherboard BIOS. Symptom 28-38. The system frequently locks up or crashes after installing a Cyrix 6x86 CPU In most cases, the Cyrix 6x86 is not being cooled prop-

erly and is overheating. Be sure that you have a heatsink/fan assembly attached attached properly to the Cyrix chip, and see that that the fan is running. Also, the Cyrix 6x86 P166+ is a 3.52-V 3.52-V CPU. Check your voltage regulator and see see that it is set to provide 3.45 to 3.6 V. Symptom 28-39. After installing a Pentium 120MHz motherboard, you get “registry corruption” or “out of memory” errors from Windows 95 This hap-

pens most often with slightly older Pentium motherboards (~100 to 120MHz), and is almost always a BIOS version problem, which causes the motherboard to m isbehave under Windows 95. You will need to update the BIOS version version for your particular motherboard. motherboard. Symptom 28-40. The motherboard fails to “auto-detect” the hard drive parameters This is a known problem on Dataexpert EXP8551S motherboards, and is

caused by a problem w ith Windows 95 in recognizing the PCI/ISA/I/O controller portion of the chipset. You can use the following procedure to force force Windows 95 to recognize the chipset properly: Boot up the Windows 95 system normally Change the directory to /WINDOWS/INF Edit the hidden file MSHDC.INF Search for all lines with the “1230” device ID. Copy the lines and replace “1230” with “7010” (the correct device ID) 5 Save the file MSHDC.INF 6 Remove the “Standard IDE/ESDI hard-disk controller” entry from the Device manager . 7 Restart the computer, then choose the Windows default driver following the instructions shown on the screen. 1 2 3 4

You should make a backup copy of the M SHDC.INF file before proceeding to edit the file. That way, you can easily restore the original file, if necessary.

If the problem persists, you should try entering the specific hard-drive parameters for your particular drive into the CMOS setup.

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Symptom 28-41. The motherboard refuses to detect the SCSI controller during bootup This problem has been identified with the Dataexpert EXP8551 moth-

erboard, but it might occur on many different types of PCI motherboards. In most cases, you will have to change the configuration of your PCI slots slots on the motherboard. For example, if the SCSI controller is installed on slot 2, you will need to configure the PCI slot 2 in CMOS setup. Symptom 28-42. A Cyrix 6x86 CPU will not run on a particular motherboard This is a problem has been identified on Eurone/Matsonic motherboards, and is

usually the result of an incompatible motherboard motherboard clock generator. Some clock generators support the Cyrix 120, 133, and 166MHz models, but exempt the 200MHz model. Other clock generators support the 120, 150, 166, and 200MHz models, but exempt the 133MHz model. So, if you’re using a 133MHz or 200MHz Cyrix CPU, you might be using the “wrong” clock generator. You will have to replace the CPU with a speed that that is suitable to the particular clock generator, or change the motherboard to one that will accommodate the particular CPU speed. Symptom 28-43. The system can only count up to and recognize 8MB of RAM, although the system can accommodate even more This problem is of-

ten identified with Freetech 586F61x motherboards using Award BIOS version D or earlier. You can duplicate the problem by initiating initiating a software reset with ++ ++ , then hitting the hardware hardware reset—BIOS will only count memory up to 8MB. 8MB. You will need to update the Award BIOS to version version E or later. Freetech provides the the BIOS patch on their Web site. Symptom 28-44. When four 8MB SIMMs are installed in the system (32MB), the system only counts up to 24MB This is a known problem with gi-

gabyte motherboards (typically (typically the GA-586ATE, ATM, and AP version version 1.x). The motherboard does not support “double-sided” SIMMs (i.e., 2MB, 8MB, 32MB, or 128MB) in the center bank. Install the SIMMs in bank 0 and bank bank 2—leaving bank 1 empty. Some motherboards require the banks to be filled in sequential order or allow you to change the bank order with jumpers. Symptom 28-45. Gold-plated SIMMs do not work properly in tin-plated sockets As a general rule, you should avoid mixing metal types when choosing

SIMMs—the metal in the SIMM socket must be the same as the metal on the SIMM itself. Otherwise, tin debris will transfer to the gold gold surface and oxidize. This will eventually result in memory failures, which suggests faulty SIMMs. Symptom 28-46. Even though all peripherals in the system are SCSI, Windows 95 will continue to detect the PCI IDE controller You notice that this oc-

curs even though the controller was disabled in CMOS. This is a known problem with the Iwill P54TS motherboard. Normally, Windows 95 will try to recognize recognize and try to enable I/O devices, but should not enable devices devices that are deliberately deliberately disabled in CMOS. This is typically a BIOS problem, so try upgrading your BIOS to the latest version.

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Symptom 28-47. An “EISA CMOS configuration error” occurs when the system starts For EISA systems, you must run the EISA configuration utility to prop-

erly set up the system. Without this step, the system will not be able to detect any possi ble resource conflicts. conflicts. This type of problem is most common when installing installing a new EISA motherboard, when CMOS contents are lost, or when devices (such as memory) are added or removed. Symptom 28-48. The SMP (dual processor) mode refuses to run in Windows NT The most common problem is an incompatibility with the SMP HAL shipped

with Windows NT (versions prior prior to 3.51) and the motherboard’s motherboard’s chipset. If you are upgrading from an older version of NT (prior to 3.51), first install NT as a standard PC (single-processor kernel), then install NT with the default multi-processor kernel that it provides (NT will not recognize your dual CPUs if you upgrade straight to a multi-processor configuration). Symptom 28-49. When attempting to upgrade your flash BIOS, an “insufficient memory” error occurs In most cases, you simply don’t have enough conventional

memory available to execute execute the flash program. Most flash programs require require about 560KB or conventional RAM. Try booting “clean” with a DOS diskette, then run the flash upgrade. Symptom 28-50. A prolonged “Updating ESCD” message appears each time that the system boots The Extended System Configuration Data (ESCD) area

is part of a PnP system. One or more PnP devices are attempting to update your your BIOS settings. To stop this from occurring, set the BIOS to “program” mode. Symptom 28-51. A yellow (!) sign appears over the USB port in the Device manager Windows 95 indicates that it it has detected an unknown PCI device. In virtu-

ally all cases, the proper driver for the USB on your system has not been installed, and Windows 95 cannot recognize the USB hardware. hardware. You can usually correct this problem problem by updating your system BIOS to a newer version that supports the USB under Windows 95. Symptom 28-52. The Device manager under Windows 95 indicates four COM ports (at unusual IRQs and I/O addresses), but only two physical ports are on the motherboard This problem has been identified with the Ocean

Rhino motherboard, which is running running a very old Award BIOS. The Award BIOS has since been upgraded to provide full support for Windows 95, so download the newest BIOS version from the motherboard manufacturer. Symptom 28-53. The performance of a motherboard with an AMD K5 CPU seems extremely poor This is almost always because of the motherboard BIOS—

chances are the BIOS was released before the AMD K5 was widely introduced, so there might be problems providing proper AMD support. Be sure that you are using the very latest BIOS that supplies adequate AMD support. Symptom 28-54. The system hangs up after installing a Cyrix 6x86 CPU

The problem is probably with the utilization of system cache, which is causing the system to hang up. Try disabling the internal (L1) and external (L2) cache.

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Symptom 28-55. When attempting to upgrade the BIOS version, a key sequence, such as +, cannot be used to reboot the PC in order to start the flash process The current BIOS version does not support such key

sequences. To flash the BIOS, start the flash flash program manually from the DOS prompt. For example: A:\> AMIFL PAIV17.ROM

Symptom 28-56. A particular SVGA board refuses to work on a particular motherboard However, the video board board proves out fine fine on other systems. systems. In most

cases, this is a compatibility compatibility problem between the video chipset and and the motherboard. A BIOS upgrade for the motherboard or video video board can overcome the problem. You might simply have to use a different video board. Symptom 28-57. When the on-board printer port is set to 3BCh (and EPP/ SPP mode) and another parallel port add-on card is set to 378h or 278h, the BIOS only recognizes the add-on card Port 3BCh seems to disappear. This

might be a configuration problem with the Winbond chipset, which specifies that LPT1 on the motherboard should be set at 378h (EPP or SPP), and add-on parallel ports should be set at 278h or 3BCh. The Winbond chip was designed this way for Windows 95. Check with the motherboard manufacturer for any available BIOS upgrades that can correct this issue. Symptom 28-58. With 32MB of RAM on the motherboard, Checkit 3.0 causes the system to reboot when performing DRAM tests This is because

Checkit 3.0 will not perform memory testing testing over 16MB. This is an issue with Checkit— not the motherboard. Upgrade to a later version of Checkit. Checkit. Symptom 28-59. The IBM Blue Lighting CPU will not run o n a motherboard that should support it In most cases, the problem problem is an older BIOS version. Be sure

that you are running the latest version of BIOS before installing the IBM Blue Lightning. Also check to be sure that any CPU type and speed jumpers are set properly for the CPU. Symptom 28-60. When using a benchmark program, such as SYSINFO, the “Overall Performance” rating of a Pentium 100 system marks better than a Pentium-120 system This is because of the PCI bus speed. For a 100MHz system,

the PCI bus speed is 33MHz. For a 120MHz system, the bus speed is 30MHz. The slightly faster PCI system will register a bit better performance. Always be sure that your benchmark and diagnostic programs are updated for the CPUs and other hardware that you are testing. Symptom 28-61. Parallel-port devices do not work on your motherboard

In most cases, you must set the proper parallel-port mode (i.e., SPP/ECP/EPP) for the particular device you plan to use. Often, setting the port to Compatibility mode will work for many common peripherals. Parallel-port modes are selected selected through the CMOS setup— usually under “Integrated peripherals” or some similar heading.

FURTHER FURTHER STUDY

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Symptom 28-62. Some configurations of memory provide less performance than others This type of problem is most noted on motherboards with 440FX

chipsets, and is usually usually the result of a BIOS problem. problem. Try updating your BIOS to the latest available version. Symptom 28-63. The performance does not improve when enabling PCI/IDE bus mastering The problem is often that you are using an older (or buggy)

driver. Be sure that you have installed the most recent bus-mastering driver file (Triton (Triton I, Triton II and Natoma chipsets might use the same driver). Symptom 28-64. The BIOS banner displayed at power-on is showing the wrong motherboard model In virtually all cases, this is a problem with the BIOS

version. Get the latest update for your motherboard motherboard BIOS. Symptom 28-65. The Pentium P55CM BIOS shows a 150MHz CPU—even though the CPU is a 166MHz model This is almost always due to a BIOS fault.

You should upgrade to the very latest latest BIOS version for your particular particular motherboard. If you cannot flash the BIOS, replace the BIOS IC outright. Symptom 28-66. “Static device resource conflict” error message occurs after the system memory count when using the P55CM CPU This problem is

usually in the PCI bus system. Press and hold the key before before turning on the com puter. Release the key when the the video comes up. This forces the system to reassign PCI resources. If the error message still appears, remove all PCI cards (except for the video card) and try again. Reinsert one PCI card at a time until the problem returns—that is where the problem is.

Further Study That’s all for Chapter 28. Be sure to review the glossary and chapter chapter questions on the accompanying CD. If you have access to the Internet, Internet, take a look at some of these mother board resources: Abit Computer Corp.: http://www.abit.com.tw/html/emain.htm Acer America Corp.: http://www.acer.com American Megatrends (AMI): http://www.megatrends.com American Predator Corp.: http://www.americanpredator.com ASUS: http://www.asus.com Biostar Microtech Intl.: http://www.biostar.net CompuTrend Systems, Inc. (Premio): http://www.premiopc.com Data Expert Corp.: http://www.dataexpert.com

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Diamond Flower, Inc. (DFI): http://www.dfiusa.com Elitegroup Computers, Ltd. (ECS): http://www.ecs.com.tw Famous Technology Co., Ltd.: http://www1.magic-pro.com.hk/famous/index.html First International Computer, Inc. (FIC): http://www.fica.com Fong Kai Industrial Co. (FKI): http://www.fkusa.com Gemlight Computer Ltd.: http://www.gemlight.com.hk Genoa Systems Corp.: http://www.genoasys.com Giga-Byte Technology Co., Ltd.: http://www.giga-byte.com Intel Corp.: http://www.intel.com Iwill Computer: http://www.iwill.com.tw Jbond: http://www.jbond.com J-Mark Computer Corp.: http://www.j-mark.com Kam-Tronic Computer Co., Ltd.: http://megastar.kamtronic.com Micronics Computers, Inc.: http://www.micronics.com Microway: http://www.microway.com Micro Star International Co., Ltd. (MSI): http://www.msi.com.tw PC Chips Manufacturing Ltd.: http://www.pcchips.com Pine Technology Ltd.: http://www.pinegroup.com Shuttle Computer International: http://www.shuttlegroup.com Soyo Computer Inc.: http://www.soyo.com.tw Supermicro Computer Inc.: http://www.supermicro.com Tekram Technology: http://www.tekram.com Tyan Computer: http://www.tyan.com

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