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BIOS PostCodes
ALR
AST
DTK
HP
IBM
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Intel Motherboards:
T440BX
VC820

  • AT&T BIOS Post Codes
  • AT&T BIOS Post Codes v3.0
  • AT&T BIOS Post Codes v3.00 - 3.03 8/26/87 286 N3.03 Extensions
  • AT&T BIOS Post Codes XT 8088/86 BIOS v3.1
  • AT&T BIOS Post Codes 386 BIOS 3.1
  • AT&T BIOS Post Codes ISA/EISA BIOS v4.0
  • AT&T BIOS Post Codes EISA BIOS
  • AT&T BIOS Post Codes late Award BIOS v4.5x-non PnP
  • AT&T BIOS Post Codes late Award BIOS v4-5x PnP

AT&T BIOS Post Codes:

01 CPU test
02 System I/O port test
03 ROM checksum test
05 DMA page register test
06 Timer 1 test
07 Timer 2 test
08 RAM refresh test
09 8/19 bit bus conversion check
0A Interrupt controller 1 test
0B Interrupt controller 2 test
0C Keyboard controller test
0D CMOS RAM/RTC test
0E Battery power test
0F CMOS RAM checksum test
10 CPU protected mode
11 Display configuration test
12 Display controller test
13 Primary display error
14 Extended CMOS test
15 AT bus reset
16 Initialize chipset registers
17 Check for extension ROM's
18 Internal memory address test
19 Remap memory
1A Memory interleave mode test
1B Remap shadow memory
1C Setup MRAM
1D Expanded memory test
1E AT memory error
1F Internal memory error
20 Minimum POST tests complete
21 DMA controller 1 test
22 DMA controller 2 test
23 Timer 0 test
24 Initialize internal controllers
25 Unexpected interrupt
26 Expected interrupt
30 Switch to protected mode
31 Size AT bus memory or size external memory
32 Address lines A16 to A23 test
33 Internal memory test or conventional memory test
34 AT bus memory test or external memory test
38 Shadow ROM BIOS to RAM
39 Shadow extension BIOS to RAM
40 Enable/disable keyboard
41 Keyboard clock and data test
42 Keyboard reset
43 Keyboard controller test
44 A20 gate test
50 Initialize interrupt table
51 Enable timer interrupt
60 Floppy controller/drive test
61 Hard disk controller test
62 Initialize floppy drives
63 Initialize hard drives
70 Real time clock test
71 Set real time clock
72 Test parallel interfaces
73 Test serial interfaces
74 Check external ROM's
75 Numeric coprocessor test
76 Enable keyboard and RTC interrupts (IRQ 9)
F0 Display system startup message
F1 Check for ROM at E000h
F2 Boot from floppy or hard disk
F3 Run setup program
F4 Run password program
FC DRAM type detection
FD CPU register test

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AT&T BIOS Post Codes v3.0:

01 CPU test 1: verify CPU status bits
02 Powerup check - Initialize motherboard and chipset with default values; Check 8042 keyboard controller buffer
03 Clear 8042 keyboard controller - send command AA, fail if status is not 2 output buffer full
04 Reset 8042 keyboard controller
05 Get8042 keyboard controller manufacturing status
06 Initialize motherboard chipset; disable color/mono video; disable 8237 DMA controller; reset 80x87 coprocessor; initialize 8255 timer 1; clear DMA/page registers/CMOS RAM shutdown byte
07 CPU test 2; read/write/verify CPU registers SS, SP, BP, with FF and 00
08 Initialize CMOS RAM/RTC
09 Checksum 32K of BIOS ROM
0A Initialize video interface; initialize 6845 controller
0B Test 8254 programmable interrupt timer channel 0
0C Test 8254 programmable interrupt timer channel 1
0D Test 8254 programmable interrupt timer channel 2
0E Test CMOS RAM shutdown byte
0F Test extended CMOS RAM, if present
10 Test 8237 DMA controller channel 0
11 Test 8237 DMA controller channel 1
12 Test 8237 DMA controller page registers
13 Test 8741 keyboard controller interface
14 Test memory refresh toggle
15 Test first 64K of base memory
16 Set up interrupt tables in low memory
17 Set up video I/O operations
18 (1 beep) Test MDA/CGA video memory unless EGA/VGA adapter is found
19 Test 8259 programmable interrupt timer channel 1
1A Test 8259 programmable interrupt timer channel 0
1B Test CMOS RAM battery level
1C Test CMOS RAM checksum
1D Set system memory size parameters
1E Size base memory 64K at a time
1F Test base memory found from 64K to 640K
20 Test stuck bit in 8259 programmable interrupt controller
21 Test for stuck NMI bits
22 Test 8259 programmable interrupt controller functionality
23 Test protected mode
24 Size extended memory above 1MB
25 Test all base and extended memory found, except the first 64K
26 Test protected mode exceptions
27 Initialize shadow RAM and move system BIOS and/or video BIOS into it if enabled by CMOS RAM setup
28 Detect and initialize Intel 8242/8248 chip
29 Reserved
2A Detect and initialize keyboard
2B Detect and initialize floppy drive
2C Detect and initialize serial ports
2D Detect and initialize parallel ports
2E Detect and initialize hard drive
2F Detect and initialize coprocessor
30 Reserved
31 Detect and initialize adapter ROM's
BD Initialize Orvonton cache controller, if present
CA Initialize 386 Micronics cache, if present
CC Shutdown NMI handler
EE Test for unexpected processor exception
FF Interrupt 19 boot loader

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AT&T BIOS Post Codes v3.00 - 3.03 8/26/87 286 N3.03 Extensions:

01 Processor test #1
02 Determine type of POST test
03 Clear 8042 keyboard controller interface
04 Reset 8042 keyboard controller interface
05 Get 8042 keyboard controller manufacturing status
06 Initialize LSI onboard chips
07 Processor test #2
08 Initialize CMOS chip
09 EPROM checksum for 32KB
0A Initialize video interface
0B Test 8254 programmable interrupt timer channel 0
0C Test 8254 programmable interrupt timer channel 1
0D Test 8254 programmable interrupt timer channel 2
0E Test CMOS date and timer
0F Test CMOS shutdown byte
10 Test DMA channel 0
11 Test DMA channel 1
12 Test DMA page registers
13 Test 8741 keyboard controller
14 Test memory refresh toggle circuits
15 Test 1st 64KB of system memory
16 Setup interrupt vector table
17 Setup video I/O operations
18 Test video memory
19 Test 8259 programmable interrupt controller channel 1 mask bits
1A Test 8259 programmable interrupt controller channel 2 mask bits
1B Test CMOS battery level
1C Test CMOS checksum
1D Setup configuration byte for CMOS
1E Sizing system memory & compare with CMOS
1F Test found system memory
20 Test stuck 8259's interrupt bits
21 Test stuck NMI bits
22 Test 8259 programmable interrupt controller functionality
23 Test protected mode and A20 gate
24 Sizing extended memory above 1MB
25 Test found system/extended memory
26 Test exceptions in protected mode
27 Reserved
2A POST_KEYBOARD
2B POST_FLOPPY
2C POST_COMM
2D POST_PRN
2E POST_DISK
2F POST_MATH
30 POST_EXCEPTION
CC POST_NMI

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AT&T BIOS Post Codes XT 8088/86 BIOS v3.1:

01 Processor test 1
02 Determine type of POST test
06 Initialize 8259 programmable interrupt controller and 8237 DMA controller chips
07 Processor test #2
09 EPROM checksum for 32KB
0A Initialize video controller 6845 registers
15 Test 1st 64K of system memory
16 Setup interrupt vector table in 1st 64K
17 Setup video I/O operations
18 Test video memory
19 Test 8259 programmable interrupt controller channel 1 mask bits
1A Test 8259 programmable interrupt controller channel 2 mask bits
1D Setup configuration byte from CMOS
1E Sizing system memory & compare with CMOS
1F Test found system memory
20 Test stuck 8259's interrupt bits
21 Test stuck NMI bits
22 Test 8259 interrupt functionality
2A Initialize keyboard
2B Initialize floppy controller and drive
2C Initialize COM ports
2D Initialize LPT ports
2F Initialize coprocessor
31 Initialize option ROM's
FF Interrupt 19 boot loader

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AT&T BIOS Post Codes 386 BIOS 3.1:

01 Processor test 1
02 Determine POST type
03 Clear 8042 keyboard controller interface
04 Reset 8042 keyboard controller interface
05 Get 8042 keyboard controller manufacturing status
06 Initialize onboard LSI chips
07 Processor test 2
08 Initialize CMOS timer/real time clock
09 EPROM checksum
0A Initialize video interface
0B Test 8254 programmable interrupt timer channel 0
0C Test 8254 programmable interrupt timer channel 1
0D Test 8254 programmable interrupt timer channel 2
0E Test CMOS shutdown byte
0F Test extended CMOS
10 Test DMA channel 0
11 Test DMA channel 1
12 Test DMA page registers
13 Test keyboard controller interface
14 Test memory refresh toggle circuits
15 Test first 64KB of system memory which is used by system BIOS
16 Setup interrupt vector table
17 Video I/O operations
18 Video memory test for CGA and mono cards
19 Test 8259 mask bits on channel 1
1A Test 8259 mask bits on channel 2
1B Check CMOS battery level
1C Test the CMOS checksum data at 2E and 2Fh
1D Configuration of CMOS if checksum good
1E System memory size determined
1F Tests memory from the top of 64K to the top of memory
20 Check for stuck 8259 interrupt bits
21 Check for stuck NMI interrupt bits
22 Check for 8259 functionality
23 Verifies protected mode
24 System memory size is determined for extended memory
25 Tests extended memory found above using virtual 8086 paging mode and writing an FFFF/AA55/0000 pattern
26 Protected mode exceptions
27 Test cache controller(386/486) or shadow RAM
28 Set up cache controller or 8042 keyboard controller
29 Reserved
2A Initialize keyboard and controller
2B Initialize floppy drive and controller
2C Detect and initialize serial ports
2D Detect and initialize parallel ports
2E Initialize hard drive and controller
2F Detect and initialize coprocessor
30 Reserved
31 Detect and initialize option ROM's
3B Initialize secondary cache with Opti chipset (486 only)
CC NMI handler shutdown
EE Unexpected processor exception
FF Interrupt 19 boot loader

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AT&T BIOS Post Codes ISA/EISA BIOS v4.0:

01 Processor test 1
02 Processor test 2
03 Calculate BIOS EPROM
04 Test CMOS RAM interface
05 Initialize chipset
06 Test memory refresh
07 Setup low memory
08 Setup interrupt vector table
09 Test CMOS RAM checksum and load default
0A Initialize keyboard
0B Initialize video interface
0C Test video memory
0D OEM specific; initialization of motherboard chips required by OEM
0E Reserved
0F Test DMA controller 0
10 Test DMA controller 1
11 DMA page registers
12 Reserved
13 Reserved
14 Test 8254 timer 0 counter 2
15 Verify 8259 programmable interrupt controller channel 1
16 Verify 8259 programmable interrupt controller channel 2
17 Test for stuck 8259 interrupt bits
18 Test 8259 functionality
19 Test for NMI bits
1A Reserved
1B Reserved
1C Reserved
1D Reserved
1E Reserved
1F Set EISA mode
20 Initialize and enable EISA slot 0
21 Initialize and enable EISA slot 1
22 Initialize and enable EISA slot 2
23 Initialize and enable EISA slot 3
24 Initialize and enable EISA slot 4
25 Initialize and enable EISA slot 5
26 Initialize and enable EISA slot 6
27 Initialize and enable EISA slot 7
28 Initialize and enable EISA slot 8
29 Initialize and enable EISA slot 9
2A Initialize and enable EISA slot 10
2B Initialize and enable EISA slot 11
2C Initialize and enable EISA slot 12
2D Initialize and enable EISA slot 13
2E Initialize and enable EISA slot 14
2F Initialize and enable EISA slot 15
30 Size base memory from 256K to 640K and test
31 Test extended memory
32 If EISA mode flag set, test EISA memory found during slot initialization
33 Reserved
34 Reserved
35 Reserved
36 Reserved
37 Reserved
38 Reserved
39 Reserved
3A Reserved
3B Reserved
3C Verify CPU can switch in and out of protected, virtual 86 and 8086 page modes
3D Check for mouse and initialize if present
3E Initialize cache controller
3F Enable shadow RAM
40 Reserved
41 Initialize floppy drive controller and drives
42 Initialize hard drive controller and hard drives
43 Serial ports detected and initialized
44 Parallel ports detected and initialized
45 Coprocessor detected and initialized
46 Setup message print to screen
47 Boot speed set
48 Reserved
49 Reserved
4A Reserved
4B Reserved
4C reserved
4D Reserved
4E If manufacturing POST loop pin set, reboot, otherwise non-fatal error messages will be displayed
4F Security check
50 Write all CMOS values back to CMOS RAM
51 Preboot enabled
52 Initialize ROM's between C80000-EFFFF
53 Initialize time value at address 40 of BIOS
55 Initialize DDNIL counter to NULL's
63 Boot attempt
B0 Spurious interrupt occurred in protected mode
B1 Unclaimed NMI
BF Program chipset
C0 OEM specific
C1 OEM specific
C2 OEM specific
C3 OEM specific
C4 OEM specific
C5 OEM specific
C6 OEM specific
C7 OEM specific
C8 OEM specific
C9 OEM specific
D0 Debug
D1 Debug
D2 Debug
D3 Debug
D4 Debug
D5 Debug
D6 Debug
D7 Debug
D8 Debug
D9 Debug
DA Debug
DB Debug
DC Debug
DD Debug
DE Debug
DF Debug
E0 Reserved
E1 Setup page 1
E2 Setup page 2
E3 Setup page 3
E4 Setup page 4
E5 Setup page 5
E6 Setup page 6
E7 Setup page 7
E8 Setup page 8
E9 Setup page 9
EA Setup page 10
EB Setup page 11
EC Setup page 12
ED Setup page 13
EE Setup page 14
EF Setup page 15
FF Boot via interrupt 19 if no errors detected

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AT&T BIOS Post Codes EISA BIOS:

01 CPU flags
02 CPU registers
03 Initialize DMA
04 Memory refresh
05 Keyboard initialization
06 ROM checksum
07 CMOS
08 256K memory
09 Cache
0A Set interrupt table
0B CMOS checksum
0C Keyboard initialization
0D Video adapter
0E Video memory
0F DMA channel 0
10 DMA channel 1
11 DMA page register
14 Timer chip
15 Programmable interrupt controller 1
16 Programmable interrupt controller 2
17 programmable interrupt controller stuck bits
18 Programmable interrupt controller maskable IRQ's
19 NMI bit check
1F CMOS RAM
20 Slot 0
21 Slot 1
22 Slot 2
23 Slot 3
24 Slot 4
25 Slot 5
26 Slot 6
27 Slot 7
28 Slot 8
29 Slot 9
2A Slot 10
2B Slot 11
2C Slot 12
2D Slot 13
2E Slot 14
2F Slot 15
30 Memory size 256K
31 Memory test over 256K
32 EISA memory
3C CMOS setup on
3D Mouse
3E Cache RAM
3F Shadow RAM
40 N/A
41 Floppy drive
42 Hard drive
43 Serial and parallel ports
45 coprocessor
47 Speed
4E manufacturing loop
4F Security
50 CMOS update
51 Enable NMI
52 Adapter ROM's
53 Set time
63 Boot
B0 NMI in protected
B1 Disable NMI
BF Chipset program
C0 Cache on/off
C1 Memory size
C2 Base 256K test
C3 DRAM page select
C4 Video switch
C5 Shadow RAM
C6 Cache program
C8 Speed switch
C9 Shadow RAM
CA OEM chipset
FF Boot

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AT&T BIOS Post Codes late Award BIOS v4.5x-non PnP:

C0 Turnoff chipset cache
01 Processor test 1
02 Processor test 2
03 Initialize chipset; Disable NMI/PIE/UEL/SQWV, video, parity checking, DMA; Reset coprocessor; Clear all page registers and CMOS shutdown byte; Initialize timer 0, 1 and 2 including EISA timer to known state; Initialize DMA controllers 0 and 1; Initialize interrupt controllers 0 and 1 and EISA extended controllers
04 Test memory refresh
05 Blank video
06 Reserved
07 Test CMOS and battery status
C1 Memory presence test
C5 Early shutdown
C6 Cache presence test
08 Setup low memory
09 Early cache initialization
0A Setup interrupt vector table; Initialize first 120 interrupt vectors with SPURIOUS_INT_HDLR and initialize interrupts 00-FF according to INT_TBL
0B Test CMOS RAM checksum
0C Initialize keyboard
0D Initialize video interface
0E Test video memory
0F Test DMA controller 0
10 Test DMA controller 1
11 Test DMA page registers
12 Reserved
13 Reserved
14 Test 8254 timer 0 counter 2
15 Test 8259 1 mask bits
16 Test 8259 2 mask bits
17 Test for 8259 stuck interrupt bits
18 Test 8259 interrupt functionality
19 Test for stuck NMI bits
1A Display CPU clock
1B Reserved
1C Reserved
1D Reserved
1E Reserved
1F Set EISA mode
20 Enable slot 0
21 Enable slot 1
22 Enable slot 2
23 Enable slot 3
24 Enable slot 4
25 Enable slot 5
26 Enable slot 6
27 Enable slot 7
28 Enable slot 8
29 Enable slot 9
2A Enable slot 10
2B Enable slot 11
2C Enable slot 12
2D Enable slot 13
2E Enable slot 14
2F Enable slot 15
30 Size base and extended memory
31 Test base and extended memory
32 Test EISA extended memory
33 Reserved
34 Reserved
35 Reserved
36 Reserved
37 Reserved
38 Reserved
39 Reserved
3A Reserved
3B Reserved
3C Setup enabled
3D Check for and initialize mouse if present
3E Setup cache controller
3F Reserved
BF Chipset initialization
40 Display virus protect enable or disable
41 Initialize floppy controller and drive's
42 Initialize hard drive controller and drive's
43 Serial and parallel ports detected and initialized
44 Reserved
45 Coprocessor detected and initialized if present
46 Reserved
47 Reserved
48 Reserved
49 Reserved
4A Reserved
4B Reserved
4C Reserved
4D Reserved
4E Manufacturing POST loop/display messages
4F Security check
50 Write CMOS
51 Preboot enable
52 Initialize options ROM's between C800 and EFFF
53 Initialize time value in 40h BIOS area
60 Setup virus protect
61 Set boot speed
62 Setup numlock
63 Boot attempt
B0 Spurious if interrupt occurs in protected mode
B1 Unclaimed NMI
E1 Setup page 1
E2 Setup page 2
E3 Setup page 3
E4 Setup page 4
E5 Setup page 4
E6 Setup page 5
E7 Setup page 6
E8 Setup page 7
E9 Setup page 8
EA Setup page 9
EB Setup page 10
EC Setup page 11
ED Setup page 12
EE Setup page 13
EF Setup page 14
FF Boot from interrupt 19

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AT&T BIOS Post Codes late Award BIOS v4-5x PnP:

C0 Turn off OEM specific cache; Initialize standard devices: DMA controller (8237), Programmable interrupt controller (8259), Programmable interval timer (8254), RTC chip
C1 Auto detection on onboard DRAM & cache
C3 Test first 256K DRAM
C5 Copy the BIOS from ROM into E000FFFF shadow RAM
01 Reserved
02 Reserved
03 Initialize EISA registers
04 Reserved
05 Keyboard controller setup; enable keyboard interface
06 Reserved
07 Verifies CMOS basic read/write functionality
BE Program default values into chipset according to the MODBINable Chipset Default Table
09 Program configuration register for Cyrix CPU according to MODBINable Cyrix Register Table; OEM specific cache initialization
0A Initialize first 32 interrupt vectors; Issue CPUID instruction to identify CPU type
0B Verify RTC; Detect bad battery; Read CMOS data into BIOS stack area; PnP initializations (PnP BIOS only): Assign CSN to PnP ISA card, create resource map from ESCD; Assign I/O and memory for PCI devices (PCI BIOS only)
0C Initialize BIOS data area
0D Program chipsets value; Measure CPU speed for display; Video initialization (If no display, speaker beeps)
0E Initialize APIC (multiprocessor BIOS only); Test video RAM; Show display message
0F DMA channel 0 test
10 DMA channel 1 test
11 DMA page registers test
12 Reserved
13 Reserved
14 Test 8254 timer 0 counter 2
15 Test 8259 interrupt mask bits for channel 1
16 Test 8259 interrupt mask bits for channel 2
17 Reserved
19 Test 8259 functionality
1A Reserved
1B Reserved
1C Reserved
1D Reserved
1E Execute EISA initialization if NVM is good
1F Reserved
20 Reserved
21 Reserved
22 Reserved
23 Reserved
24 Reserved
25 Reserved
26 Reserved
27 Reserved
28 Reserved
29 Reserved
30 Size base and extended memory
31 Test base memory from 256K to 640K; Test extended memory from 1MB to the top of memory
32 Display Award Plug & Play BIOS Extension message; Program super I/O chipset
33 Reserved
34 Reserved
35 Reserved
36 Reserved
37 Reserved
38 Reserved
39 Reserved
3A Reserved
3B Reserved
3C Set flag to allow access to CMOS setup
3D Initialize keyboard; Initialize PS/2 mouse
3E Initialize L2 cache
3F Reserved
40 Reserved
BF Program chipset values according to setup
41 Initialize floppy controller and floppy drives
42 Initialize hard drive controller and hard drives
43 initialize serial and parallel ports in PnP BIOS
44 Reserved
45 Initialize coprocessor
46 Reserved
47 Reserved
48 Reserved
49 Reserved
4A Reserved
4B Reserved
4C Reserved
4D Reserved
4E Error messages displayed if detected (F1 displayed to continue)
4F Ask for password if needed; Energy star logo displayed if Green BIOS
50 Write all CMOS values currently in the BIOS stack back to the CMOS
51 Reserved
52 Initialize ISA ROM's; Assign IRQ's to any PCI devices, initialize PCI ROM's; PnP initializations; Shadow RAM setup; Parity setup; Power management initialized
53 Serial and parallel ports initialized for non-PnP BIOS
54 Reserved
55 Reserved
56 Reserved
57 Reserved
58 Reserved
59 Reserved
5A Reserved
5B Reserved
5C Reserved
5D Reserved
5E Reserved
5F Reserved
50 Virus protection setup for boot sector if enabled
61 L2 cache enabled; Boot up speed according to setup; Chipset initialization finalized; Power Management finalized; Show system configuration table
62 Setup time/date according to setup values; Program the numlock, typematic rates, and typematic speeds according to setup
63 ESCD updated if changed to BIOS made; Clear memory that may be used; Bot from interrupt 19
FF Boot

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All information has been gathered with permission of the respective BIOS providers. Although Bios Central has used reasonable effort to ensure accuracy we are unable to verify all codes posted. Use at your own risk. Bios Central, or any person associated with Bios Central takes no responsibility for any dmage resulting from the use of this information.


Copyright © 1988 -  by Bob Hurt. All rights reserved. Bios Central is a trademark of Bob Hurt.

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