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AT&T VER 3.0 BIOS POST Codes

  • 01 - CPU test 1: verify CPU status bits
  • 02 - Power-up 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 - 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
  • 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
  • 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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