Upgrading and Repairing PCs

PC Diagnostics

This chapter describes several levels of diagnostic software that are either included with your system or available from your system manufacturer as well as third parties. The chapter describes how you can get the most from this software. It also details the various ROM BIOS audio codes and error codes and examines aftermarket diagnostics and public-domain diagnostic software.

Diagnostics Software

Several types of diagnostic software are available for PCs. Some diagnostic functions are integrated into the PC hardware or into peripheral devices, such as expansion cards, whereas others take the form of operating system utilities or separate software products. This software, some of which is included with the system when purchased, assists users in identifying many problems that can occur with a computer's components. In many cases, these programs can do most of the work in determining which PC component is defective or malfunctioning. The types of diagnostic software are as follows:

• POST. The power on self test operates whenever any PC is powered up (switched on). These routines are contained within the motherboard ROM as well as ROMs on expansion cards.

• Manufacturer supplied diagnostics software. Many of the larger manufacturers—especially high-end, name-brand manufacturers such as IBM, Hewlett-Packard, Dell, and others—make special diagnostics software expressly designed for their systems. This manufacturer-specific software normally consists of a suite of tests that thoroughly examines the system. In some cases, these utilities are included with the system, or you can download these diagnostics from the manufacturer's online services at no charge; otherwise, you might have to purchase them. Many vendors include a limited version of one of the aftermarket packages that has been customized for use with their systems. In some older IBM and Compaq systems, the diagnostic software is installed on a special partition on the hard drive and can be accessed during startup. This was a convenient way for those system manufacturers to ensure that users always had diagnostics available.

• Peripheral diagnostics software. Many hardware devices ship with specialized diagnostics software designed to test their particular functions. Adaptec SCSI host adapters, for example, include diagnostic functions in the card's ROM BIOS that you can access with a keystroke (Ctrl+A) at boot time. Sound cards normally include a diagnostic program on a disk along with the drivers, which test and verify all the card's functions. Network adapters usually include a diagnostic specific to that adapter on a disk, also normally with the drivers. Other devices or adapters also might provide a diagnostic program or disk, usually included with the drivers for the device.

• Operating system diagnostics software. Operating systems, such as Windows 9x/Me and Windows NT/2000/XP, include a variety of diagnostic software utilities designed to identify and monitor the performance of various components in the computer.

• Aftermarket diagnostics software. A number of manufacturers make general-purpose diagnostics software for PCs. This type of software is often bundled with other system maintenance and repair utilities to form a general PC software toolkit.

The Power On Self Test

When IBM first began shipping the original PC in 1981, it included safety features that had never been seen in a personal computer. These features were the power on self test (POST) and parity-checked memory. Although parity-checked or even error correcting code (ECC) memory is no longer available in most low-end chipsets, every PC still executes a POST when you turn it on. The following sections provide more detail on the POST, a series of program routines buried in the motherboard ROM-BIOS chip that tests all the main system components at power-on time. This series of routines is partially responsible for the delay when you turn on your PC; the computer executes the POST before loading the operating system.

What Is Tested?

Whenever you start up your computer, it automatically performs a series of tests that checks the primary components in your system, such as the CPU, ROM, motherboard support circuitry, memory, and major peripherals such as the expansion chassis. These tests are brief and are designed to catch hard (not intermittent) errors. The POST procedures are not very thorough compared with available disk-based diagnostics. The POST process provides error or warning messages whenever it encounters a faulty component.

Although the diagnostics performed by the system POST are not very thorough, they are the first line of defense, especially when it comes to detecting severe motherboard problems. If the POST encounters a problem severe enough to keep the system from operating properly, it halts the system boot process and generates an error message that often identifies the cause of the problem. These POST-detected problems are sometimes called fatal errors because they prevent the system from booting.

How Are Errors Displayed?

The POST tests normally provide three types of output messages: audio codes, onscreen text messages, and hexadecimal numeric codes that are sent to an I/O port address.

POST errors can be displayed in the following three ways:

• Beep codes. Heard through the speaker attached to the motherboard.

• POST checkpoint codes. Hexadecimal checkpoint codes sent to an I/O port address. A special card plugged into either an ISA or a PCI card slot is required to view these codes.

• Onscreen messages. Error messages displayed onscreen after the video adapter is initialized.

BIOS POST Beep Codes

Beep codes are used for fatal errors only, which are errors that occur so early in the process that the video card and other devices are not yet functional. Because no display is available, these codes take the form of a series of beeps that identify the faulty component. When your computer is functioning normally, you should hear one short beep when the system starts up at the completion of the POST, although some systems (such as Compaq's) beep twice at the end of a normal POST. If a problem is detected, a different number of beeps sounds, sometimes in a combination of short and long tones.

BIOS POST Checkpoint Codes

POST checkpoint codes are hexadecimal numeric codes written by POST routines to I/O port address 80h as each major step is begun. These are often simply called POST codes. These POST codes can be read by only a special adapter card plugged into one of the system slots. These cards originally were designed for system manufacturers to use for burn-in testing of the motherboard. Several companies make these cards available to technicians. Micro 2000, JDR Microdevices, Data Depot, Ultra-X, and Trinitech are just a few manufacturers that market these POST cards. See the vendor list on the DVD for more information about these manufacturers.

POST checkpoint codes can be used to track the system's progress through the boot process from power-on right up to the point at which the bootstrap loader runs (when the operating system load begins). When you plug a POST code reader card into a slot, during the POST you will see two-digit hexadecimal numbers flash on the card's display. If the system stops unexpectedly or hangs, you can identify the test that was in progress during the hang from the two-digit code. This step usually helps to identify the malfunctioning component.

Most older POST reader cards plug into the 8-bit connector that is a part of the ISA or EISA bus. Many systems—even those with PCI slots—still have ISA connectors. In that case, those cards are adequate. However, the motherboards found in most newer PCs have no ISA slots at all, so obviously an ISA POST card won't work. Virtually all the companies that make POST cards also make PCI versions. Micro 2000 has a card called the Post-Probe, which has both ISA and PCI connectors on the same board. PCWiz has a similar card called the PCISA FlipPOST (see Figure 23.1). Both companies also have separate Micro Channel Architecture (MCA) bus adapters that allow POST cards to work in older IBM PS/2 systems with the MCA bus.

No matter what, be sure your POST card works in a PCI slot if you are working on modern PCs. Most newer systems don't have ISA slots, and you will rarely encounter any MicroChannel slots. If you maintain older Compaq or EISA-based systems from any vendor, these systems might use an I/O port address other than port 80. Simpler POST cards monitor only port 80, but more sophisticated cards (such as the PCISA FlipPOST shown in Figure 23.1) have DIP switches or jumper blocks to configure the card to monitor the different I/O port addresses used by Compaq and EISA-based systems.

Note Listings for additional POST checkpoint codes can be found in the Technical Reference section of the DVD. Also, see Chapter 5, "BIOS," to learn more about working with your BIOS. Remember to consult your motherboard documentation for codes specific to your BIOS version. Also, the documentation included with the various POST cards covers most older as well as newer BIOS versions.

BIOS POST Onscreen Messages

Onscreen messages are brief messages that attempt to indicate a specific failure. These messages can be displayed only after the point at which the video adapter card and display have been initialized.

These different types of error messages are BIOS dependent and vary among BIOS manufacturers, and even in some cases among different BIOSs from the same manufacturer. The following sections list the codes used by the most popular ROM BIOS versions (AMI, Award, Phoenix, and IBM BIOS), but you should consult your motherboard or ROM BIOS manufacturer for the codes specific to your board and BIOS.

Most POST code cards come with documentation listing the POST checkpoint codes for various BIOS versions. If your BIOS is different from what I have listed here, consult the documentation for your BIOS or the information that came with your particular POST card.

Note I've also included additional BIOS error messages in the Technical Reference section on the DVD included with this book.

AMI BIOS POST Error Codes

Table 23.1. AMI BIOS POST Beep Codes

Beeps	Error Description	Action
1	Memory Refresh Error	Clean the memory contacts and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
2	Memory Parity Error	Clean the memory contacts and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
3	Base 64KB Memory Error	Clean the memory contacts and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
4	Timer Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
5	Processor Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Make sure the processor and heatsink are installed properly; remove and reseat them. Replace the processor. Replace the motherboard.
6	8042 – Gate A20 Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the keyboard, motherboard, and processor.
7	Processor Exception Interrupt Error	Make sure the processor and heatsink are installed properly; remove and reseat them. Replace the processor. Replace the motherboard.
8	Display Memory Read/Write Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
9	ROM Checksum Error	Try reseating the motherboard ROM chip. Try reflashing the motherboard ROM. Replace the motherboard.
10	CMOS Shutdown Register Read/Write Error	Replace the CMOS battery. Replace the motherboard.
11	Cache Memory Bad	Make sure cache settings in BIOS Setup are properly configured. Replace the processor. Replace the motherboard.
1 long, 3 short	Conventional/Extended Memory Error	Clean the memory contacts and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
1 long, 8 short	Display/Retrace Error	Check the video card for proper installation. Try replacing the video card memory. Replace the video card. Replace the motherboard.
AMI BIOS codes used by permission of American Megatrends, Inc.

If you have a POST card, you can find the AMI BIOS POST checkpoint codes in the Technical Reference section of the DVD packaged with this book.

Award BIOS and Phoenix FirstBIOS POST Error Codes

Currently, only one standard beep code exists in the Award BIOS (also known as the Phoenix FirstBIOS). A single long beep followed by two short beeps indicates that a video error has occurred and that the BIOS cannot initialize the video screen to display any additional information. If multiple or continuous beeps occur with an Award BIOS, this usually indicates problems with the power supply or memory.

Table 23.2. Award BIOS/Phoenix FirstBIOS POST Beep Codes

Beeps	Error Description	Action
1 long, 2 short	Video Card Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
1 long, 3 short	Video Card Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
Continuous beeps	Memory Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.

If you have a POST card, you can find the Award BIOS and Phoenix FirstBIOS POST checkpoint codes in the Technical Reference section of the DVD packaged with this book.

Table 23.3. Award BIOS POST Onscreen Error Messages

Message	Description
BIOS ROM checksum error - System halted	The checksum of the BIOS code in the BIOS chip is incorrect, indicating the BIOS code might have become corrupt. Contact your system dealer to replace the BIOS.
CMOS battery failed	The CMOS battery is no longer functional. Contact your system dealer for a replacement battery.
CMOS checksum error - Defaults loaded	Checksum of CMOS is incorrect, so the system loads the default equipment configuration. A checksum error can indicate that CMOS has become corrupt. This error might have been caused by a weak battery. Check the battery and replace if necessary.
CPU at nnnn	Displays the running speed of the CPU.
Display switch is set incorrectly	The display switch on the motherboard can be set to either monochrome or color. This message indicates the switch is set to a different setting than indicated in Setup. Determine which setting is correct, and then either turn off the system and change the jumper or enter Setup and change the VIDEO selection.
Press ESC to skip memory test	The user can press Esc to skip the full memory test.
Floppy disk(s) fail	Can't find or initialize the floppy drive controller or the drive. Make sure the controller is installed correctly. If no floppy drives are installed, be sure the Diskette Drive selection in Setup is set to NONE or AUTO.
HARD DISK initializing. Please wait amoment	Some hard drives require extra time to initialize.
HARD DISK INSTALL FAILURE	Can't find or initialize the hard drive controller or the drive. Make sure the controller is installed correctly. If no hard drives are installed, be sure the Hard Drive selection in Setup is set to NONE.
Hard disk(s) diagnosis fail	The system might run specific disk diagnostic routines. This message appears if one or more hard disks return an error when the diagnostics run.
Keyboard error or no keyboard present	Can't initialize the keyboard. Make sure the keyboard is attached correctly and no keys are pressed during POST. To purposely configure the system without a keyboard, set the error halt condition in Setup to HALT ON ALL, BUT KEYBOARD. The BIOS then ignores the missing keyboard during POST.
Keyboard is locked out - Unlock the key	This message usually indicates that one or more keys have been pressed during the keyboard tests. Be sure no objects are resting on the keyboard.
Memory Test:	This message displays during a full memory test, counting down the memory areas being tested.
Memory test fail	If POST detects an error during memory testing, additional information appears giving specifics about the type and location of the memory error.
Override enabled - Defaults loaded	If the system can't boot using the current CMOS configuration, the BIOS can override the current configuration with a set of BIOS defaults designed for the most stable, minimal-performance system operations.
Press TAB to show POST screen	System OEMs might replace Phoenix Technologies' AwardBIOS POST display with their own proprietary displays. Including this message in the OEM display permits the operator to switch between the OEM display and the default POST display.
Primary master hard disk fail	POST detects an error in the primary master IDE hard drive.
Primary slave hard disk fail	POST detects an error in the secondary master IDE hard drive.
Resuming from disk, Press TAB to showPOST screen	Phoenix Technologies offers a save-to-disk feature for notebook computers. This message might appear when the operator restarts the system after a save-to-disk shutdown.
Secondary master hard disk fail	POST detects an error in the primary slave IDE hard drive.
Secondary slave	POST detects an error in the secondary slave IDE hard hard disk fail drive.

Phoenix BIOS POST Error Codes

The following beep codes are for the current version of Phoenix BIOS, version 4.0, release 6.1. Other versions have somewhat different beeps and Port 80h codes.

Table 23.4. Phoenix BIOS 5.x and Earlier POST Beep Codes

Beeps	Error Description	Action
1-2	Video Card Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
1-3	CMOS RAM Read/Write Error	Replace the CMOS battery. Replace the motherboard.
1-1-4	ROM Checksum Error	Try reseating the motherboard ROM chip. Try reflashing the motherboard ROM. Replace the motherboard.
1-2-1	Timer Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
1-2-2	DMA Initialization Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
1-2-3	DMA Page Register Read/Write Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
1-3-1	RAM Refresh Verification Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
1-3-3	First 64KB RAM Multibit Data Line Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
1-3-4	First 64KB RAM Odd/Even Logic Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
1-4-1	First 64KB RAM Address Line Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory, power supply, and motherboard.
1-4-2	First 64KB RAM Parity Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
2-?-?	First 64KB RAM Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
3-1-1	Slave DMA Register Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
3-1-2	Master DMA Register Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
3-1-3	Master Interrupt Mask Register Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
3-1-4	Slave Interrupt Mask Register Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
3-2-4	Keyboard Controller Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the keyboard. Replace the motherboard. Replace the processor.
3-3-4	Screen Initialization Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
3-4-1	Screen Retrace Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
3-4-2	Video ROM Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.
4-2-1	Timer Interrupt Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
4-2-2	Shutdown Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the keyboard. Replace the motherboard. Replace the processor.
4-2-3	Gate A20 Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the keyboard. Replace the motherboard. Replace the processor.
4-2-4	Unexpected Interrupt In Protected Mode	Check for a bad expansion card. Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
4-3-1	RAM Address Error >FFFh	Clean the memory contacts, reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
4-3-3	Interval Timer Channel 2 Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
4-3-4	Real Time Clock Error	Replace the CMOS battery. Replace the motherboard.
4-4-1	Serial Port Error	Reset the port configuration in BIOS Setup. Disable the port.
4-4-2	Parallel Port Error	Reset the port configuration in BIOS Setup. Disable the port.
4-4-3	Math Coprocessor Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Make sure the processor and heatsink are installed properly; remove and reseat them. Replace the processor. Replace the motherboard.
Low 1-1-2	System Board Select Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Make sure the processor and heatsink are installed properly; remove and reseat them. Replace the processor. Replace the motherboard.
Low 1-1-3	Extended CMOS RAM Error	Replace the CMOS battery. Replace the motherboard.

Table 23.5. Phoenix BIOS 6.x and Later POST Beep Codes

Beeps	Error Description	Description/Action
1-2-2-3	BIOS ROM Checksum Error	Try reseating the motherboard ROM chip. Try reflashing the motherboard ROM. Replace the motherboard.
1-3-1-1	DRAM Refresh Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
1-3-1-3	8742 Keyboard Controller Error	Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the keyboard. Replace the motherboard. Replace the processor.
1-3-4-1	Memory Address Line Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
1-3-4-3	Memory Low Byte Data Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
1-4-1-1	Memory High Byte Data Error	Clean the memory contacts, and reseat the modules. Remove all modules except the first bank. Replace the memory. Replace the power supply. Replace the motherboard.
2-1-2-3	ROM Copyright Error	Try reseating the motherboard ROM chip. Try reflashing the motherboard ROM. Replace the motherboard.
2-2-3-1	Unexpected Interrupts	Check for a bad expansion card. Check for proper motherboard installation, loose screws, foreign objects causing shorts, and over-tightened screws. Replace the motherboard.
1-2	Video Card Error	Check the video card for proper installation. Try replacing the video card memory, and replace the video card. Replace the motherboard.

If you are using a POST card, you can find the Phoenix BIOS POST codes in the Technical Reference section of the DVD packaged with this book.

IBM BIOS POST Error Codes

Table 23.6. IBM BIOS Beep Codes

Audio Code	Sound Graph	Description
1 short beep	•	Normal POST—system okay
2 short beeps	••	POST error—error code on display
No beep		Power supply, system board
Continuous beep	—————	Power supply, system board
Repeating short beeps	••••	Power supply, system board
	••
1 long, 1 short beep	-•	System board
1 long, 2 short beeps	-••	Video adapter (MDA/CGA)
1 long, 3 short beeps	-•••	Video adapter (EGA/VGA)
3 long beeps	- - -	3270 keyboard card
IBM BIOS beep and Alphanumeric error codes used by permission of IBM.

Table 23.7. IBM BIOS POST/Diagnostics Display Error Codes

Code	Description
1xx	System board errors
2xx	Memory (RAM) errors
3xx	Keyboard errors
4xx	Monochrome Display Adapter (MDA) errors
4xx	PS/2 system board parallel port errors
5xx	Color Graphics Adapter (CGA) errors
6xx	Floppy drive/controller errors
7xx	Math Coprocessor errors
9xx	Parallel printer adapter errors
10xx	Alternate parallel printer adapter errors
11xx	Primary Async Communications (Serial COM1:) errors
12xx	Alternate Async Communications (Serial COM2:, COM3:, and COM4:) errors
13xx	Game control adapter errors
14xx	Matrix printer errors
15xx	Synchronous Data Link Control (SDLC) Communications adapter errors
16xx	Display Station Emulation Adapter (DSEA) errors (5520, 525x)
17xx	ST-506/412 fixed disk and controller errors
18xx	I/O expansion unit errors
19xx	3270 PC attachment card errors
20xx	Binary Synchronous Communications (BSC) adapter errors
21xx	Alternate Binary Synchronous Communications (BSC) adapter errors
22xx	Cluster adapter errors
23xx	Plasma monitor adapter errors
24xx	Enhanced graphics adapter (EGA) or video graphics array (VGA) errors
25xx	Alternate Enhanced Graphics Adapter (EGA) errors
26xx	XT or AT/370 370-M (memory) and 370-P (processor) adapter errors
27xx	XT or AT/370 3277-EM (emulation) adapter errors
28xx	3278/79 emulation adapter or 3270 connection adapter errors
29xx	Color/graphics printer errors
30xx	Primary PC network adapter errors
31xx	Secondary PC network adapter errors
32xx	3270 PC or AT display and programmed symbols adapter errors
33xx	Compact printer errors
35xx	Enhanced display station emulation adapter (EDSEA) errors
36xx	General-purpose interface bus (GPIB) adapter errors
37xx	System board SCSI controller errors
38xx	Data acquisition adapter errors
39xx	Professional graphics adapter (PGA) errors
44xx	5278 display attachment unit and 5279 display errors
45xx	IEEE interface adapter (IEEE-488) errors
46xx	A real-time interface coprocessor (ARTIC) multiport/2 adapter errors
48xx	Internal modem errors
49xx	Alternate internal modem errors
50xx	PC convertible LCD errors
51xx	PC convertible portable printer errors
56xx	Financial communication system errors
70xx	Phoenix BIOS/chipset unique error codes
71xx	Voice communications adapter (VCA) errors
73xx	3 1/2'' external disk drive errors
74xx	IBM PS/2 display adapter (VGA Card) errors
74xx	8514/A display adapter errors
76xx	4216 PagePrinter adapter errors
84xx	PS/2 speech adapter errors
85xx	2MB XMA memory adapter or XMA adapter/A errors
86xx	PS/2 pointing device (mouse) errors
89xx	Musical Instrument Digital Interface (MIDI) adapter errors
91xx	IBM 3363 write-once read multiple (WORM) optical drive/adapter errors
96xx	SCSI adapter with cache (32-bit) errors
100xx	Multiprotocol adapter/A errors
101xx	300/1200bps internal modem/A errors
104xx	ESDI or MCA IDE fixed disk or adapter errors
107xx	5 1/4'' external disk drive or adapter errors
112xx	SCSI adapter (16-bit without cache) errors
113xx	System board SCSI adapter (16-bit) errors
129xx	Processor complex (CPU board) errors
149xx	P70/P75 plasma display and adapter errors
152xx	XGA display adapter/A errors
164xx	120MB internal tape drive errors
165xx	6157 streaming tape drive or tape attachment adapter errors
166xx	Primary Token-Ring network adapter errors
167xx	Alternate Token-Ring network adapter errors
180xx	PS/2 wizard adapter errors
185xx	DBCS Japanese display adapter/A errors
194xx	80286 memory-expansion option memory-module errors
200xx	Image adapter/A errors
208xx	Unknown SCSI device errors
209xx	SCSI removable disk errors
210xx	SCSI fixed disk errors
211xx	SCSI tape drive errors
212xx	SCSI printer errors
213xx	SCSI processor errors
214xx	SCSI write-once read multiple (WORM) drive errors
215xx	SCSI CD-ROM drive errors
216xx	SCSI scanner errors
217xx	SCSI magneto optical drive errors
218xx	SCSI jukebox changer errors
219xx	SCSI communications errors
243xxxx	XGA-2 adapter/A errors
I998xxxx	Dynamic configuration select (DCS) information codes
I99900xx	Initial microcode load (IML) error
I99903xx	No bootable device, initial program load (IPL) errors
I99904xx	IML-to-system mismatch
I99906xx	IML (boot) errors
IBM BIOS beep and alphanumeric error codes used by permission of IBM.

POST Memory Count

On some PCs, the POST also displays the results of its system memory test on the monitor. The last number displayed is the amount of memory that tested successfully. For example, a system might display the following message:

32768 KB OK

The number displayed by the memory test should agree with the total amount of memory installed on the system motherboard. Some older systems display a slightly lower total because they deduct part or all of the 384KB of UMA (upper memory area) from the count. On old systems that use expanded memory cards, the memory on the card is not tested by the POST and does not count in the numbers reported. Also, this memory test is performed before any system software loads, so many memory managers or device drivers you might have installed do not affect the results of the test. If the POST memory test stops short of the expected total, the number displayed can indicate how far into the system memory array a memory error lies. This number can help you identify the exact module that is at fault and can be a valuable troubleshooting aid in itself.

Hardware Diagnostics

Many types of diagnostic software are used with specific hardware products. This software can be integrated into the hardware, included with the hardware purchase, or sold as a separate product. The following sections examine several types of hardware-specific diagnostics.

Note IBM included specialized diagnostic software for its older PS/2 systems. For more information on this software, see "IBM Diagnostics," in Upgrading and Repairing PCs, Sixth Edition on the DVD-ROM included with this book.

SCSI Diagnostics

Unlike the IDE drive support that is built into the system BIOS of virtually every PC, SCSI is an add-on technology, and most SCSI host adapters contain their own BIOS that enables you to boot the system from a SCSI hard drive. In some cases, the SCSI BIOS also contains configuration software for the adapter's various features, and diagnostics software as well.

The most popular manufacturer of SCSI host adapters is Adaptec, and most of its host adapters contain these features. An Adaptec SCSI adapter normally includes a BIOS that can be enabled or disabled. When the BIOS is activated, you see a message on the monitor as the system boots, identifying the model of the adapter and the revision number of the BIOS. The message also instructs you to press Ctrl+A to access what Adaptec calls its SCSISelect utility.

The SCSISelect utility identifies the Adaptec host adapters installed in the system and, if more than one exists, enables you to choose the adapter you want to work with by selecting its port address.

After you do this, you are presented with a menu of the functions built into the adapter's BIOS. Every adapter BIOS contains a configuration program and a SCSI Disk Utilities feature that scans the SCSI bus, identifying the devices connected to it. For each hard disk drive connected to the bus, you can perform a low-level disk format or scan the disk for defects, remapping any bad blocks that are found.

For SCSI adapters that use direct memory access (DMA), a Host Adapter Diagnostics feature is also available, which tests the communication between the adapter and the main system memory array by performing a series of DMA transfers. If this test fails, you are instructed how to configure the adapter to use a lower DMA transfer rate.

Network Interface Diagnostics

As with SCSI adapters, many network interface adapters are equipped with their own diagnostics, designed to test their own specialized functions. Depending on the network adapter, these tests might require you to boot with a DOS disk, or they might function within Windows.

The DIAG program included with all Linksys network interface cards, for example, performs the following internal tests on the Linksys EtherFast 10/100 Ethernet adapter:

• Configuration test

• I/O test

• ID test

• Internal Loopback test

• Link Status test

• Interrupt test

• Network Function test

The Network Function test sequence requires that you have another node installed on the same network with a Linksys adapter. By running the Diag software on both computers, you can configure one adapter to send data and the other to be the receiver. The sender transmits test messages to the receiver, which echoes the same messages back again. If the adapters and network are functioning properly, the messages should return to the sending system in exactly the same form as they were transmitted.

Other network adapters have similar testing capabilities, although the names of the tests might not be exactly the same. The software for the 3Com 3C509B adapter, for example, performs the following tests:

• Register Access test

• EEPROM Vital Data test

• EEPROM Configurable Data test

• FIFO Loopback test

• Interrupt test

• Ethernet Core Loopback test

• Encoder/Decoder Loopback test

• Echo Exchange test (requires two adapters on the same network)

The Linksys EtherFast 10/100 network adapter is a PCI PnP adapter, but the disk included with the adapter provides the driver files needed for Windows and other operating systems, as well as the diagnostics program. The 3Com 3C509B is an ISA card that must be configured by the diagnostics program if you want to use a switchless installation, or you can configure the card with DIP switches.

If you do not have the driver or diagnostics files for your network adapter, you can normally download them free of charge from the manufacturers' respective Web sites.

General-Purpose Diagnostics Programs

A large number of professional third-party diagnostics programs are available for PC systems. These are commercial programs that are used by technicians to perform testing of new systems (often called burn-in testing) or testing of existing systems either in the shop or in the field.

Most of the commercial PC diagnostics can test all your PC's key components. In addition, specific programs are available to test memory, floppy drives, hard disks, video adapters, and most other areas of the system. Some of the programs I recommend most highly include

• AMIDiag Suite. See www.ami.com for more information.

• MicroScope. See www.micro2000.com for more information.

Tip Before trying a commercial diagnostic program to solve your problem, look in your operating system. Most operating systems today provide at least some of the diagnostic functions that diagnostic programs do. You might be able to save some time and money.

Unfortunately, no clear leader exists in the area of diagnostic software. Each program has unique advantages, and as a result, no program is universally better than another. When deciding which diagnostic programs, if any, to include in your arsenal, look for the features you need.

One of the most popular is AMIDiag from AMI. This program runs on virtually any PC and tests most of the hardware in the system. AMIDiag is available in a native Windows version that also supports third-party diagnostics modules or in a DOS version that can be used to test hardware, regardless of the operating system, by using a DOS boot disk to start the system.

Note The DVD included with this book contains a breakdown of some of the PC diagnostics software available today. See the Technical Reference section of the DVD.

Operating System Diagnostics

In many cases, it might not be necessary to purchase third-party diagnostic software because your operating system has all the diagnostic tools you need. Windows 9x/Me and NT/2000/XP include a large selection of programs that enable you to view, monitor, and troubleshoot the hardware in your system.

Note The DVD included with this book contains a breakdown of some of the operating-system-diagnostics software available today. See the Technical Reference section of the DVD.