IBM Corporation IBM AT BIOS P.O. Box 1328 =========== Boca Raton, FL 33429 00 Not defined 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