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