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Appendix A BIOS POST Codes
One long and two short beeps – video configuration error
One repetitive long beep – no memory detected
Terminal POST Errors
If a terminal type of error occurs, BIOS will shut down the system. Before doing so, BIOS
will write the error to port 80h, attempt to initialize video and write the error in the top left
corner of the screen.
The following is a list of codes that may be written to port 80h.
Terminal POST Errors
Code
Description
02h
Verify Real Mode
03h
Disable Non-Maskable Interrupt (NMI)
04h
Get CPU type
06h
Initialize system hardware
07h
Disable shadow and execute code from the ROM.
08h
Initialize chipset with initial POST values
09h
Set IN POST flag
0Ah
Initialize CPU registers
0Bh
Enable CPU cache
0Ch
Initialize caches to initial POST values
0Eh
Initialize I/O component
0Fh
Initialize the local bus IDE
10h
Initialize Power Management
11h
Load alternate registers with initial POST values
12h
Restore CPU control word during warm boot
13h
Initialize PCI Bus Mastering devices
14h
Initialize keyboard controller
16h
1-2-2-3 BIOS ROM checksum
17h
Initialize cache before memory Auto size
18h
8254 timer initialization
1Ah
8237 DMA controller initialization
1Ch
Reset Programmable Interrupt Controller