Technical data

Server Management
4-6
POST Codes and Countdown Codes
The BIOS indicates the current testing phase during POST after the video
controller has been successfully initialized by outputting a 2-digit hex code to I/O
location 80h. There are two different sets of codes:
•
Codes displayed during the normal BIOS POST process
•
Codes displayed during the recovery boot process
Normal Port-80 Codes and Countdown Codes
Port 80
Codes
Countdown
Codes
Description
D0h Early MP initialization, enter real mode
D1h Power on initialization
D2h Disable NMI
D3h Reset video controller
D4h Enter real mode
D5h Checksum the 8 KB loader BIOS
D6h Loader BIOS checksum good
D7h 900 Check if keyboard controller (KBC) buffers are free
D8h Issue BAT (basic assurance test) command to KBC
D9h Read BAT results
DAh Check if KBC passed BAT
DBh 820 Keyboard initialization passed
DDh Disable keyboard and auxiliary devices
DFh Disable both DMA controllers
E0h 780 Preliminary initialization of PICs
E1h Enter real big mode and initialize chipset, size memory
E2h Initialize timer 2 for speaker
E3h 760 Initialize timer channel 0 for system timer
E4h Clear any pending parity errors
continued