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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
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