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AT&T 386 BIOS 3.1 BIOS Post Codes

  • 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
  • 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
  • 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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