Chips & Technologies Post Procedures
 Power on tests   CPU synchronizes with clock.  Check the CPU or clock if a failure occurs 
 System ROM Check   The BIOS runs a checksum on itself.   Check the BIOS chips if a failure occurs 
 DMA controller Fail   DMA controllers are initialized and tested.  Check the DMA chips if a failure occurs 
 System Timer Failed   Channels 0, 1, and 2 are tested in sequence.  If a failure occurs, check the PIT chips 
 Base 64K Memory Testing   Walking bit test performed on first 64K of RAM which is critical for the BIOS vector area to be initialized.  Check for bad RAM chips or a bad data or address line 
 Interrupt Controller Failed   Test the 8259 chip 
 CPU Still In Protected Mode   Attempts are made to read the configuration of the system through the 8042 keyboard controller 
 Refresh Not Occurring   Memory refresh is tested; standard refresh is 120-140ns.  Check the PIT if a failure occurs 
 Keyboard Controller Not Responding   Tests are run on the keyboard controller.  the the KBC 8042 if a failure occurs 
 Could Not Enter Protected Mode   BIOS attempts to enter protected mode to test extended memory.  Check the 8042 KBC chip or the A20 gate address line if a failure occurs 
 Initialize Timer   Attempts are made to initialize the PIT 
 Initialize DMA Controller   Attempts are made to initialize the DMA controllers 
 Entering/Exiting Protected Mode   The translation is handled by the keyboard controller and the A20 gate address line.  Check the keyboard controller if a failure occurs 
 Relocate Shadow RAM   BIOS attempts to shadow itself into extended memory.  Check for memory problems if a failure occurs 
 Test For EMS   Check for EMS adapter or an improper CMOS setting/Jumper setting if a failure occurs 
 Test Video Capabilities   Normally includes a memory test on the adapter memory up to 256K 
 Test Memory   Extensive testing of Base, Extended,and Expanded memory.  Check for defective memory modules, 8042 KBC, A20 gate address line or an improper CMOS and/or jumper setting 
 Check System Options   The hardware in the system is compared with the values stored in CMOS.  The PIT, PIC, 8042 KBC, RTC and other system board components are tested again 
 Peripheral Check and test   Checks are made for the peripherals at standard I/O ports including serial and parallel ports, keyboards, and math coprocessor.   You should see an error message on screen at the point if a failure occurs 
 Floppy Test   Floppy devices set in CMOS are checked and initialized.  If a bootable floppy is found the fixed disks are tested and the BIOS will boot to the floppy disk.  Check for defective controllers or an improper CMOS Setup if a failure occurs 
 Fixed Disk Test   Checks for fixed disks in CMOS.  If no bootable floppy in the A: drive, then the BIOS loads the first sector off the first fixed disk and jumps to the area of memory where the sector was loaded.  You may just see a flashing cursor or an error message from the potential operating system.  Check for improper CMOS Setup, defective controller, or fixed disk failure.  Also, check for a corrupt bootloader on the fixed disk 
 Advanced Options   These include the mouse, cache, etc..   you should see an error message on the screen at this point, except that a defective cache may hang the system.  In most cases, the cache will be disabled by the BIOS 
Chips & Technologies BIOS Post Codes
 00   Error in POS register 
 01   CPU flag register failed 
 02   CPU register test failed 
 03   BIOS ROM checksum failed 
 04   DMA controller test failed 
 05   System timer IC failed 
 06   Base 64K RAM failed address test: not installed, misconfigured, or bad addressing 
 07   Base 64K RAM failed data test 
 08   Interrupt controller failed 
 09   Hot (unexpected) interrupt occurred 
 0A   System timer does not interrupt 
 0B   CPU still in protected mode 
 0C   DMA page registers failed 
 0D   Refresh not occurring 
 0E   Keyboard controller not responding 
 0F   Could not enter protected mode 
 10   GDT or IDT failed, Keyboard controller failed 
 11   LDT register failed, Keyboard controller failed 
 12   Task register failed, Keyboard controller failed 
 13   LSL instruction failed, keyboard controller failed 
 14   LAR register failed, Keyboard controller failed 
 15   VERR/VERW failed, Keyboard controller failed 
 16   Keyboard controller gate A20 failed 
 17   Exception failed/unexpected exception 
 18   Shutdown during memory test 
 19   Last used error code 
 1A   Copyright checksum error 
 1B   Shutdown during memory sizing 
 1C   Chipset initialization 
 50   Initialize hardware 
 51   Initialize timer 
 52   Initialize DMA controller 
 53   Initialize 8259 programmable interrupt controller 
 54   Initialize system chipset 
 55   Setup EMS configuration 
 56   Entering protected mode for first time 
 57   Size memory chips 
 58   Configure memory chip interleave 
 59   Exiting protected mode for first time 
 5A   Determine system board memory size 
 5B   Relocate shadow RAM 
 5C   Configure EMS 
 5D   Set up wait state configuration 
 5E   Re-test 64K RAM 
 5F   Test shadow RAM 
 60   Test CMOS RAM 
 61   Test video 
 62   Test and initialize DDNIL bits 
 63   Test protected mode interrupt 
 64   Test address line A20 
 65   Test memory address lines 
 66   Test memory 
 67   Test extended memory 
 68   Test timer interrupt 
 69   Test real time clock (RTC) 
 6A   Test keyboard 
 6B   Test 80x87 math chip 
 6C   Test RS232 serial ports 
 6D   Test parallel ports 
 6E   Test dual card 
 6F   Test floppy drive controller 
 70   Test hard drive controller 
 71   Test keylock 
 72   Test pointing device 
 90   Setup RAM 
 91   Calculate CPU speed 
 92   Check configuration 
 93   Initialize BIOS 
 94   POST Bootstrap 
 95   Reset IC's 
 96   PEAK: System board POS.   NEAT/OC8291 ELEAT: Test /initialize cache RAM and controller. 
 97   VGA power on diagnostics and setup 
 98   Adapter BIOS 
 99   Re-initialize DDNIL bits 
 A0   Exception 0 
 A1   Exception 1 
 A2   Exception 2 
 A3   Exception 3 
 A4   Exception 4 
 A5   Exception 5 
 A6   Exception 6 
 A7   Exception 7 
 A8   Exception 8 
 A9   Exception 9 
 AA   Exception A 
 AB   Exception B 
 AC   Exception C 
 AD   Exception D 
 C0   System board memory failure 
 C1   I/O channel check activated 
 C2   Watchdog timer timeout 
 C3   Bus timer timeout