IBM AT BIOS Post Codes
- 01 - CPU Register Read/Write Test Failed
- 02 - CMOS RAM Read/Write Test Failed
- 03 - ROM BIOS Checksum Error
- 04 - 8253 Timer Channel 1 All Bits OFF Failure
- 05 - 8253 Timer Channel 1 All Bits ON Failure
- 06 - 8237 DMA 0 Register Test Failure
- 07 - 8237 DMA 1 Register Test Failure
- 08 - DMA Page Register Test Failure
- 09 - Memory Refresh Test Failure
- 0A - 8042 Keyboard Controller Test - Step 1
- 0B - 8042 Keyboard Controller Test - Step 2
- 0C - 8042 Keyboard Controller Test - Step 3
- 0D - 8042 Keyboard Controller Test - Step 4
- 0E - Base 64K RAM Read/Write Storage Test - Step 1
- 0F - Base 64K RAM Read/Write Storage Test - Step 2
- DD - Base 64K Error, Followed by Failing Bit Pattern, High then Low
- 11 - Verify 286 LGDT/SGDT and LIDT/SIDT Instructions
- 12 - Protected Mode Test Failure
- 13 - 8259 Interrupt Initialization
- 14 - Interrupt Vector Initialization
- 15 - Establish BIOS Subroutine Call Interrupt Vectors
- 16 - Check CMOS Battery Condition
- 17 - CMOS Checksum Error
- 18 - Enable Protected Mode
- 19 - Set Return Address Byte in CMOS
- 1A - Protected Mode Test
- 1B - Second 64K Memory Test
- 1C - Determine Memory Size 512K / 640K
- 1D - Determine Memory Size Above 1024K
- 1E - Set RAM Size in CMOS
- 1F - Test Address Lines 19-23
- 20 - Fatal Addressing Error
- 21 - Check CMOS Configuration Data
- 22 - Video Card Initialization Failure or Invalid Switch Setting
- 23 - Advanced Video Card Initialization Failure or Invalid Switch Setting
- 24 - 8259 Interrupt Mask Register All Bits OFF Test
- 25 - 8259 Interrupt Mask Register All Bits ON Test
- 26 - Check for Unexpected Interrupts, 101 System Error
- 27 - System Board Logic Failure, 106 System Error
- 28 - Non Maskable Interrupt Failure, 107 System Error
- 29 - 8253 Timer Register Failure, 108 System Error
- 2A - 8253 Timer Speed Failure, 102 System Error
- 2B - 8253 Timer Interrupt Initialization
- 2C - 8253 Timer 0 Interrupt Failure, 103 System Error
- 2D - 8042 Keyboard Controller Failure, 105 System Error
- 2F - Check for Warm Boot
- 30 - Protected Mode Read/Write Memory Test - Step 1
- 31 - Protected Mode Read/Write Memory Test - Step 2
- 33 - Protected Mode Read/Write Memory Test - Step 3
- 34 - Protected Mode Read/Write Memory Test - Step 4
- 35 - Check for Manufacturing Burn In Test
- 36 - Keyboard Clock Error
- 37 - Keyboard Failure - Test 1
- 38 - Keyboard Failure - Test 2
- 39 - Keyboard Failure - Test 3
- 3A - Keyboard Locked
- 3B - Check for Optimal Video ROM
- 3C - Floppy Diskette Adaptor Test
- 3D - Floppy Disk Drive Initialization
- 3E - Hard Disk Drive Initialization
- 3F - Any Non-Fatal Error, Press F1 to Continue
- 40 - Math Coprocessor Initialization
- 41 - Transfer For System Code at Segment E000:0
- 42 - Transfer Control to System Code
- 43 - POST Complete, Passing Control to INT 19H Boot Loader
- 90 - Unexpected Interrupt
- 91 - Unexpected Interrupt
- 92 - Unexpected Interrupt
- 93 - Unexpected Interrupt
- 94 - Unexpected Interrupt
- 95 - Unexpected Interrupt
- 96 - Unexpected Interrupt
- 97 - Unexpected Interrupt
- 98 - Unexpected Interrupt
- 99 - Unexpected Interrupt
- 9A - Unexpected Interrupt
- 9B - Unexpected Interrupt
- 9C - Unexpected Interrupt
- 9D - Unexpected Interrupt
- 9E - Unexpected Interrupt
- 9F - Unexpected Interrupt
- A0 - Unexpected Interrupt
- A1 - Unexpected Interrupt
- A2 - Unexpected Interrupt
- A3 - Unexpected Interrupt
- A4 - Unexpected Interrupt
- A5 - Unexpected Interrupt
- A6 - Unexpected Interrupt
- A7 - Unexpected Interrupt
- A8 - Unexpected Interrupt
- A9 - Unexpected Interrupt
- AA - Unexpected Interrupt
- AB - Unexpected Interrupt
- AC - Unexpected Interrupt
- AD - Unexpected Interrupt
- AE - Unexpected Interrupt
- AF - Unexpected Interrupt
- B0 - Unexpected Interrupt
- B1 - Unexpected Interrupt
- B2 - Unexpected Interrupt
- B3 - Unexpected Interrupt
- B4 - Unexpected Interrupt
- B5 - Unexpected Interrupt
- F0 - Various Additional Protected Mode Tests
- F1 - Interrupt Test
- F2 - Exception Interrupt Test
- F3 - Verify 286 LDT/SDT and LTR/STR Instructions
- F4 - Verify 286 Bound Instruction
- F5 - Stack/Register Test
- F6 - Verify Access Rights Function Correctly
- F7 - Verify Adjust RPL Field of Selector Instruction (ARPL) Functions
- F8 - Check the LAR Instruction
- F9 - Check the LSL (Load Segment Limits)
- FA - Low MEG Chip Select Test