Port 80H Post Codes; Port 80H Codes - Intel MS440GX Product Manual

Port 80h POST Codes

During the POST, the BIOS generates diagnostic progress codes (POST codes) to I/O port 80h. If
the POST fails, then execution stops and the last POST code generated is left at port 80h. This
code is useful for determining the point where an error occurred.
Displaying the POST codes requires an add-in card (often called a POST card). The POST card
can decode the port and display the contents on a medium such as a seven-segment display. These
cards can be purchased from JDR Microdevices or other sources.
The following table provides the POST codes that can be generated by the BIOS. Some codes are
repeated in the table because that code applies to more than one operation.
Table 64.

Port 80h Codes

Code Description of POST Operation
02h Verify real mode
03h Disable non-maskable interrupt (NMI)
04h Get processor type
06h Initialize system hardware
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 valuesnew
12h Restore CPU control word during warm boot
13h Initialize PCI bus mastering devices
14h Initialize keyboard controller
16h BIOS ROM checksum
17h Initialize cache before memory autosize
18h 8254 timer initialization
1Ah 8237 DMA controller initialization
1Ch Reset programmable interrupt controller
20h Test DRAM refresh
22h Test keyboard controller
24h Set ES segment register to 4 GB
26h Enable A20 line
28h Autosize DRAM
29h Initialize POST memory manager
Error Messages
Continued
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