Appendix B: BIOS POST Checkpoint Codes
B-3 Uncompressed Initialization Codes
The following runtime checkpoint codes are listed in order of execution. These codes are uncompressed in F0000h shadow RAM.
Checkpoint
03h
05h
06h
07h
08h
0Ah
0Bh
0Ch
0Eh
0Fh
10h
11h
12h
13h
14h
19h
1Ah
2Bh
2Ch
2Dh
23h
24h
Code Description
The NMI is disabled. Next, checking for a soft reset or a power on condition.
The BIOS stack has been built. Next, disabling cache memory.
Uncompressing the POST code next.
Next, initializing the CPU and the CPU data area.
The CMOS checksum calculation is done next.
The CMOS checksum calculation is done. Initializing the CMOS status register for date and time next.
The CMOS status register is initialized. Next, performing any required initialization before the keyboard BAT command is issued.
The keyboard controller input buffer is free. Next, issuing the BAT command to the keyboard controller.
The keyboard controller BAT command result has been verifi ed. Next, performing any necessary initialization after the keyboard controller BAT command test.
The initialization after the keyboard controller BAT command test is done. The key- board command byte is written next.
The keyboard controller command byte is written. Next, issuing the Pin 23 and 24 blocking and unblocking command.
Next, checking if <End or <Ins> keys were pressed during power on. Initializing CMOS RAM if the Initialize CMOS RAM in every boot AMIBIOS POST option was set in AMIBCP or the <End> key was pressed.
Next, disabling DMA controllers 1 and 2 and interrupt controllers 1 and 2.
The video display has been disabled. Port B has been initialized. Next, initializing the chipset.
The 8254 timer test will begin next.
Next, programming the fl ash ROM.
The memory refresh line is toggling. Checking the 15 second on/off time next.
Passing control to the video ROM to perform any required confi guration before the video ROM test.
All necessary processing before passing control to the video ROM is done. Look- ing for the video ROM next and passing control to it.
The video ROM has returned control to BIOS POST. Performing any required pro- cessing after the video ROM had control
Reading the 8042 input port and disabling the MEGAKEY Green PC feature next. Making the BIOS code segment writable and performing any necessary confi gura- tion before initializing the interrupt vectors.
The confi guration required before interrupt vector initialization has completed. In- terrupt vector initialization is about to begin.
