ComputingAviationOrderingUpdatesSitesContact
 
Home  
 
"The computer book of the month is The Bios Companion by Phil Croucher. Long-time readers of this column will recall I have recommended his book before. This tells you everything you ought to know about the BIOS in your system. Post codes, options, upgrades, you name it.

Years ago, I called an earlier edition of this invaluable and I see no reason to change my view. Recommended."

Jerry Pournelle
Byte Magazine

"Croucher's book was invaluable 20 years ago and remains so today...... Every one of the 468 pages holds useful information, the author having zero tolerance for padding."

Davey Winder
PC Plus Magazine

"You've completerly impressed me with the quality and scope of your guides - extreme care has obviously gone into their research and preparation."

Jeremy Fleming

"His style is lovely: clear, jargon-free where possible, chatty and friendly with beautiful short paragraphs. It [Communications & Networks] joins my list of 'I wish I'd written it' books. I haven't come across such a good subject book in a long time at this price."

Lorna Kyle
Personal Computer World

"To any micro owner who wants to know what this comms business is all about, [Communications & Networks] is certainly one of the best around. ... Croucher is not only knowledgable about his subject, he's interested in it and communicates that interest to you. "

Ron Peck
New Computer Express

"There are few books about which explain as accurately and comprehensively as [Communications & Networks] does what communications are all about. The glossary is excellent."

Micro Decision

"...any PC user with a genuine interest in using his machine to its full potential will recognise [Communications & Networks] for the completely invaluable tool and often the inspiration that it is."

Yvonne Taylor
Which PC

"[Communications & Networks] is the type of book you can read on a bus or train without getting a headache from trying to understand what it means."

Network

"As a recently reformed computer illiterate myself, I appreciated the author's straighforward yet humourous and light-hearted style of writing. He manages to strike the balance between too much and too little information. ... [Computing Under Protest] is never in danger of either boring or confusing the reader."

Emma Tyrrall
Practical PC

"Good documentation is important for any software, but even more so for an operating system - the documentation [for DOS 386 Professional] has some exceptionally clear explanations. Altogether, the documentation is an example of the right way of doing things, and other software manufacturers would do well to take note."

Matthew Holbrook
Computer Shopper

"The DOS 386 Professional manual sets arrived at 2130 local time today. We have had a brief look at them and wish to congratulate IMS on the excellent, clear and concise manner in which they have been presented."

Fred Parker
ETL Soft

"I remain impressed by Mr. Croucher's fluid writing style, practical orientation, enthusiasm, and strong technical knowledge."

Lance A Leventhal
Slawson Communications, Inc



JAR Professional Pilot Studies

"Its real value lies in taking the plethora of booklets and ring-bound photocopies associated with commercial examinations and condensing them into an attractive and portable form. The guy really does deserve a medal ~ he has made a genuine contribution to the body of professional aviation literature assembled during the course of the last century.

I heartily recommend it to students of commercial flight, if only as a souvenir of their efforts... "

Colin Hilton
Pro Pilot's Rumour Network

"(The) Book is quite a good compliment to our notes for students. We will be recommending all our students buy the books.... "

Chris
Naples Air Centre

"I got your book last month and am in the process of ploughing through it! Actually, I really like it and find it very interesting and easy to read."

Simon Rouse

"So far I have found your book an extremely helpful reference manual to carry around in my flight bag."

Blair Clubley

"I wish to commend you on a "work of art". I wish the CAA would produce a quick reference easy to read manual such as yours. Truly wonderful!"

Ebrahim Parkar
 
Post Codes
 Acer
 ALR
 AMI
 Arche
 AST
 AT&T
  Award
 Chips & Technologies
 Compaq
 Dell
 DTK
 Eurosoft/Mylex
  Faraday A-Tease
 HP
 IBM
 Intel
 Landmark
 Microid/MR
 NCR 		 Olivetti
 Philips
 Phoenix
 Quadtel
 Supersoft
 Tandon
 Zenith

AMI POST Codes

Note: Not all POST codes are included below - the latest information is in the The BIOS Companion, which contains over 100 pages of them.


POST Procedures - Feb 91

NMI Disable NMI interrupt line to the CPU is disabled by setting bit 7 I/O port 70h (CMOS)
Power On Delay Once the keyboard controller gets power, it sets the hard and soft reset bits.  Check the keyboard controller or clock generator if a failure occurs
Initialize Chipsets Check the BIOS, CLOCK and chipsets
Reset Determination The BIOS reads the bits in the keyboard controller to see if a hard or soft reset is required (a soft reset will not test memory above 64K).  Failure could be the BIOS or keyboard controller
ROM BIOS Checksum The BIOS performs a checksum on itself and adds a preset factory value that should make it equal to 00.  If a failure occurs, check the BIOS chips
Keyboard Test A command is sent to the 8042 keyboard controller which performs a test and sets a buffer space for commands.  After the buffer is defined the BIOS sends a command byte, writes data to the buffer, checks the high order bits of the internal keyboard controller and issues a No Operation (NOP) command
CMOS Shutdown byte in CMOS RAM offset 0F is tested, the BIOS checksum calculated and diagnostic byte 0E updated before the CMOS RAM area is initialized and updated for date and time.  Check the RTC and CMOS chip or battery if a failure occurs
DMA (8237) and PIC (8259) Disable The DMA and Programmable Interrupt Controller are disabled before the POST proceeds and further.  Check the 8237 or 8259 chips if a failure occurs
Video Disable The video controller is disabled and port B initialized.  Check the video adapter if a failure occurs
Chipset Initialized and Memory Detected Memory addressed in 64K blocks.   Failure would be in the chipset.  If all memory is not seen, failure could be in a chip in the block after the last one seen
PIT Test The timing functions of the 8254 Programmable Interrupt Timer are tested.  The PIT and RTC chips normally cause errors here
Memory Refresh PIT's ability to refresh memory is tested.  If an XT, DMA controller #1 handles this.  Failure is normally the PIT (8254) in AT's or the 8237, DMA #1, in XT's
Address Line Test the address lines in the first 64K of RAM.  If a failure occurs, an address line may be the problem
Base 64K Data patterns are written to the first 64K of RAM, unless there is a bad RAM chip in which case you will get a failure
Chipset Initialization The PIT, PIC and DMA controllers are initialized
Set Interrupt Table Interrupt vector table used by PIC is installed in low memory, the first 2K
8042 Keyboard Controller Check The BIOS reads the buffer area in the keyboard controller I/O port 60.  Failure here is normally the keyboard controller
Video Tests The type of video adapter is checked for, then a series of tests are performed on the adapter and monitor
BIOS Data Area The vector table is checked for proper operation and video memory verified before protected mode tests are entered into.   This is done so that any errors found are displayed on the monitor
Protected Mode Tests Perform reads and writes to all memory locations below 1MB.  Failure at this point indicate a bad RAM chip, the 8042 Keyboard Controller or a data line
DMA Chips The DMA registers are tested using a data pattern
Final Initialization these differ with each version.   Typically, the floppy and hard drives are tested and initialized and a check is made for serial and parallel devices.  The information gathered is then compared against the contents of the CMOS and you will see the results of any failures on the monitor
BOOT The BIOS hands over control to the Int 19 bootloader.  This is where you would see error messages such as non-system disk

Back to Top


 Text Messages

Bad PnP Serial ID Checksum The Serial ID checksum of a PnP card is invalid
Floppy Disk Controller Resource Conflict The floppy drive controller had requested a resource that is already in use
NVRAM Checksum Error - NVRAM Cleared The extended system configuration data (ESCD) was reinitialized because of an NVRAM checksum error.  Clear CMOS and ESCD RAM and reboot
NVRAM Cleared By Jumper The Clear CMOS jumper has been moved to the Clear position.  CMOS RAM and ESCD have been cleared
NVRAM Data Invalid - NVRAM Cleared Invalid data found in the ESCD, which might mean that you have changed devices in the system.  When this message is displayed, the BIOS has already rewritten the ESCD with current configuration data
Parallel Port Resource Conflict The parallel port requested a resource that is already in use
PCI Error Log is Full More than 15 PCI conflict errors have been detected and no additional PCI errors can be logged
PCI I/O Port Conflict Two devices requested the same I/O address, resulting in a conflict
PCI IRQ Conflict Two devices requested the same IRQ, resulting in a conflict
PCI Memory Conflict Two devices requested the same memory resource, resulting in a conflict
Primary Boot Device Not Found Two designated primary boot device (hard disk, floppy disk drive, CD-ROM drive) could not be found
Primary IDE Controller Resource Conflict The primary IDE controller has requested a resource that is already in use
Primary Input Device Not Found The designated primary input device (keyboard, mouse, or other device if input is redirected) could not be found
Secondary IDE Controller Resource Conflict The secondary IDE controller has requested a resource that is already in use
Serial Port 1 Resource Conflict Serial port 1 has requested a resource that is already in use
Serial Port 2 Resource Conflict Serial port 2 has requested a resource that is already in use
Static Device Resource Conflict A card that is not Plug-and-Play ISA has requested a resource that is already in use
System Board Device Resource Conflict A card that is not Plug-and-Play ISA has requested a resource that is already in use
A20 Error Gate A20 on the keyboard controller is not working
Address line Short Error in the address decoding circuitry on the motherboard
CMOS Battery State Low The battery power is low; replace the battery
CMOS Checksum Invalid After CMOS RAM values are saved, a checksum value is generated for error checking.  The previous value is different from the current value
Run Setup CMOS system options not set.  The values stored in CMOS RAM are either corrupt or nonexistent.  Run Setup
CMOS Display Type Mismatch The video type in CMOS RAM does not match the type detected by the BIOS. Run Setup
CMOS Memory Size Mismatch The amount of memory on the motherboard is different from the amount indicated in CMOS RAM.  Run Setup
CMOS Time and Date Not Set run Setup to set the time and date in the CMOS RAM
Diskette Boot Failure The boot disk in drive A: is corrupt.  It cannot be used to boot the system.  Use another boot disk and follow the screen instructions
DMA Error Error in the DMA controller
DMA #1 Error Error in the first DMA controller
DMA #2 Error Error in the second DMA controller
FDD Controller Failure The BIOS cannot communicate with the floppy disk drive controller.   Check all appropriate cables and connections
HDD Controller Failure The BIOS cannot communicate with the hard disk drive controller.   Check all appropriate cables and connections
Insert Bootable Media The BIOS cannot find a bootable medium.  Insert a bootable floppy disk or CD-ROM
INTR #1 Error Interrupt controller 1 failed POST
INTR #2 Error Interrupt controller 2 failed POST
Invalid Boot Diskette The BIOS can read the disk in floppy drive A:, but cannot boot the system from it.  Use another boot disk
KB/Interface Error There is an error in the keyboard connector
Keyboard Error There is a timing problem with the keyboard
Keyboard Stuck Key Detected A stuck keyboard key was detected
Off Board Parity Error Parity error in memory installed in an expansion slot.  The format is: OFF BOARD PARITY ERROR ADDR (HEX) = (XXXX), where XXXX is the hex address where the error occurred
On Board Parity Error Parity error in memory installed on the motherboard.  The format is: ON BOARD PARITY ERROR ADDR (HEX) = (XXXX), where XXXX is the hex address where the error occurred
Parity Error Parity error in system memory at an unknown address
System halted An error caused the computer to halt
Timer Channel 2 Error There is an error in counter/timer 2
Uncorrectable ECC Error An uncorrectable ECC memory error was detected
Undetermined NMI An undetermined NMI was detected
Memory parity Error at xxxxx Memory failed.  If the memory location can be determined, it is displayed as xxxxx.  If not, the message is Memory Parity Error ????.
I/O Card Parity Error at xxxxx An expansion card failed.  If the address can be determined, it is displayed as xxxxx.  if not, the message is I/O Card Parity error ????
DMA Bus Timeout A device has driven the bus signal for more than 7.8 microseconds

Back to Top


 POST Codes Pre April 1990

01 NMI is disabled and the i286 register test is about to start
02 i286 register test has passed
03 ROM BIOS checksum test (32Kb from F8000h) passed OK
04 8259 programmable interrupt controller has initialized OK
05 CMOS interrupt disabled
06 Video system disabled and the system timer checks OK
07 8253/4 programmable-interval timer test OK
08 Delta counter channel 2 OK
09 Delta counter channel 1 OK
0A Delta counter channel 0 OK
0B Parity status cleared
0C The refresh and system timer check OK
0D Refresh check OK
0E Refresh period checks OK
10 Ready to start 64KB base memory test
11 Address line test OK
12 64KB base memory test OK
13 System-interrupt vectors initialized
14 8042 keyboard controller checks OK
15 CMOS read/write test OK
16 CMOS checksum and battery OK
17 Monochrome video mode OK
18 CGA color mode set OK
19 Attempting to pass control to video ROM at C0000h
1A Returned from video ROM
1B Display memory read/write test OK
1C Display memory read/write alternative test OK
1D Video retrace test OK
1E Global equipment byte set for proper video operation
1F Ready to initialize video system
20 Video test OK
21 Video display OK
22 The power-on message is displayed
30 Ready to start the virtual-mode memory test
31 virtual memory mode test started
32 CPU has switched to virtual mode
33 Testing the memory address lines
34 Testing the memory address lines
35 Lower 1MB of RAM found
36 Memory size computation checks OK
37 Memory test in progress
38 Memory below 1MB is initialized
39 Memory above 1MB is initialized
3A Memory size is displayed
3B Ready to test the lower 1MB of RAM
3C Memory test of lower 1MB OK
3D Memory test above 1MB OK
3E Ready to shutdown for real-mode testing
3F Shutdown OK- now in real mode
40 Ready to disable gate A20
41 A20 line disabled successfully
42 Ready to start DMA controller test
4E Address line test OK
4F System still in real mode
50 DMA page register test OK
51 Starting DMA controller 1 register test
52 DMA controller 1 test passed, starting DMA controller 2 register test
53 DMA controller 2 test passed
54 Ready to test latch on DMA controller 1 and 2
55 DMA controller 1 and 2 latch test OK
56 DMA controller 1 and 2 configured OK
57 8259 programmable interrupt controller initialized OK
58 8259 programmable interrupt controller mask register OK
59 Master 8259 programmable interrupt controller mask register OK
5A Ready to check timer interrupts
5B Timer interrupt check OK
5C Ready to test keyboard interrupt
5D Error detected in timer or keyboard interrupt
5E 8259 programmable interrupt controller error
5F 8259 programmable interrupt controller OK
70 Start of keyboard test
71 Keyboard controller Ok
72 Keyboard tested OK
73 Keyboard global initialization OK
74 Floppy setup ready to start
75 Floppy controller setup OK
76 Hard disk setup ready to start
77 Hard disk controller setup OK
79 Ready to initialize timer data
7A Verifying CMOS battery power
7B CMOS battery verified OK
7D Analyzing CMOS RAM size
7E CMOS memory size updated
7F Send control to adapter ROM
80 Enable the setup routine if <Delete> is pressed
82 Printer data initialization is OK
83 RS-232 data initialization is OK
84 80x87 check and test OK
85 Display any soft-error message
86 Give control to ROM E0000h
87 Return from system ROM
00 Call the Int19 boot loader

Back to Top


POST Codes After April 1990

 

01 NMI is disabled and the i286 register test is about to start
02 i286 register test has passed
03 ROM BIOS checksum test (32KB from E8000h) passed OK
04 Passed keyboard controller test with and without mouse
05 Chipset initialized...DMA and interrupt controller disabled
06 Video system disabled and the system timer checks OK
07 8254 programmable interval timer initialized
08 Delta counter channel 2 initialization complete
09 Delta counter channel 1 initialization complete
0A Delta counter channel 0 initialization complete
0B Refresh started
0C System timer started
0D Refresh check OK
10 Ready to start 64KB base memory test
11 Address line test OK
12 64KB base memory test OK
15 ISA BIOS interrupt vectors initialized
17 Monochrome video mode OK
18 CGA color mode set OK
19 Attempting to pass control to video ROM at C0000h
1A Returned from video ROM
1B Shadow RAM enabled
1C Display memory read/write test OK
1D Alternate display memory read/write test OK
1E Global equipment byte set for proper
1F Ready to initialize video system
20 Finished setting video mode
21 ROM type 27256 verified
22 The power-on message is displayed
30 Ready to start the virtual mode memory test
31 Virtual memory mode test started
32 CPU has switched to virtual mode
33 Testing the memory address lines
34 Testing the memory address lines
35 Lower 1MB of RAM found
36 Memory size computation checks OK
37 Memory test in progress
38 Memory below 1MB is initialized
39 Memory above 1MB is initialized
3A Memory size is displayed
3B Ready to test the lower 1MB of RAM
3C Memory test of lower 1MB OK
3D Memory test above 1MB OK
3E Ready to shutdown for real-mode testing
3F Shutdown Ok - now in real mode
40 Cache memory now on...Ready to disable gate A 20
41 A20 line disabled successfully
42 i486 internal cache turned on
43 Ready to start DMA controller test
50 DMA page register test OK
51 Starting DMA controller 1 register test
52 DMA controller 1 test passed, starting DMA controller 2 register test
53 DMA controller 2 test passed
54 Ready to test latch on DMA controller 1 and 2
55 DMA controller 1 and 2 latch test OK
56 DMA controller 1 and 2 configured OK
57 8259 programmable interrupt controller initialized Ok
70 Start of keyboard test
71 Keyboard controller OK
72 Keyboard test OK...Starting mouse interface test
73 Keyboard and mouse global initialization OK
74 Display setup prompt.. Floppy setup ready to start
75 Floppy controller setup OK
76 hard disk setup ready to start
77 Hard disk controller setup OK
79 Ready to initialize timer data
7A Timer data area initialized
7B CMOS battery verified OK
7E CMOS memory size updated
7F Enable setup routine if <Delete> is pressed
80 Send control to adapter ROM at C800h to DE00h
81 Return from adapter ROM
82 Printer data initialization is OK
83 RS-232 data initialization is OK
84 80x87 check and test OK
85 Display any soft error message
86 Give control to ROM at E0000h
A0 Program the cache SRAM
A1 Check for external cache
A2 initialize EISA adapter card slots
A3 Test extended NMI in EISA system
00 Call the INT19 boot loader

Back to Top


2.2 BIOS

 

00 Flag test; Testing of the CPU
03 Register test
06 Chipset test; System hardware initialized
09 BIOS checksum tested
0C Page register tested
0F 8254 timer tested
12 Memory refresh initialization
15 8237 DMA controllers tested
18 8237 DMA initialization
1B 8259 PIC initialization
1E 8259 PIC chips tested
21 Memory refresh tested
24 Base 64 address tested
27 Base 64 memory tested
2A 8742 keyboard tested
2D MC146818 RTC/CMOS
30 Protected mode started
33 Memory sizing test
36 First protected mode test passed
39 First protected mode test failed
3C CPU speed calculation
3F Read 8742 hardware switches
42 Initialize interrupt vector area
45 Verify CMOS configuration
48 Test and initialize video system
4B Unexpected interrupt tested
4E Start second protected mode test
51 Verify LDT instruction
54 Verify TR instruction
57 Verify LSL instruction
5A Verify LAR instruction
5D Verify VERR instruction
60 Address line A20 test
63 Unexpected exception tested
66 Start third protected mode test
69 Address line tested
6A Scan DDNIL bits for null pattern
6C System memory tested
6F Shadow memory tested
72 Extended memory tested
75 Verify memory configuration
78 Display CMOS error messages
7B Copy system BIOS shadow memory
7E 8254 clock tested
81 MC146818 RTC tested
84 Keyboard test
87 Determine keyboard type
8A Stuck key test
8D Initialize hardware Interrupt vectors
90 Math co-processor tested
93 Determine COM ports available
96 Determine LPT ports available
99 Initialize BIOS data area
9C Fixed/floppy controller tested
9F Floppy disk tested
A2 Fixed disk tested
A5 External ROM screen; Check for external ROM's
A8 System key lock test
AE F1 error message test
AF System boot initialization
B1 Call to Interrupt 19 boot loader

Back to Top


AMI Plus BIOS

 

00 Control to Interrupt 19
01 NMI disabled (Bit 7 of I/O port 70h)
02 286 register test over
03 ROM checksum OK
04 8259 PIC initialization disabled
05 CMOS Interrupt disabled
06 System timer (PIT) counting OK
07 Channel 0 of 8259 PIC test OK
08 DMA channel 2 of delta count test OK
09 DMA channel 1 of delta count test OK
0A DMA channel 0 of delta test count OK
0B Parity status cleared (DMA/PIT)
0C Refresh and system time check OK (DMA/PIT)
0D Refresh link toggling OK (DMA/PIT)
0E Refresh period ON/OFF 50% OK
10 About to start 64K memory
11 Address line tested OK
12 64K base memory tested OK
13 Interrupt vectors initialized
14 8042 keyboard controller tested
15 CMOS Read/Write test OK
16 CMOS checksum/battery tested
17 Monochrome mode set OK (6845)
18 Color (CGA) mode set OK (6845)
19 Video ROM search
1A Optional video ROM OK
1B Display memory Read/Write test OK
1C Alternate display memory OK
1D Video retrace check Ok
1E Global byte set for video Ok
1F Mode set for mono/color OK
20 Video test OK
21 Video