Chapter 4 60
POST Task Routines
The following is a list of the Test Point codes written to port 80h at the start of each routine, the beep codes
issued for terminal errors, and a description of the POST routine. Unless otherwise noted, these codes are
valid for PhoenixBIOS.
NOTE: The following routines are sorted by their test point numbers assigned in the BIOS code. Their actual
oder as executed during POST can be quite different.
Code Beeps POST Routine Description
02h Verify Real Mode
03h Disable Non-Maskable Interrupt (NMI)
04h Get CPU 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 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 autosize
18h 8254 timer initialization
1Ah 8237 DMA controller initialization
1Ch Reset Programmable Interrupt Controller
20h 1-3-1-1 Test DRAM refresh
22h 1-3-1-3 Test 8742 Keyboard Controller
24h Set ES segment register to 4 GB
26h Enable A20 line
28h Autosize DRAM
29h Initialize POST Memory Manager
2Ah Clear 512 KB base RAM
2Ch 1-3-4-1 RAM failure on address line xxxx*
2Eh 1-3-4-3 RAM failure on data bits xxxx* of low byte of memory bus
2Fh Enable cache before system BIOS shadow
30h 1-4-1-1 RAM failure on data bits xxxx* of high byte of memory bus
32h Test CPU bus-clock frequency
33h Initialize Phoenix Dispatch Manager
36h Warm start shut down
38h Shadow system BIOS ROM
3Ah Autosize cache
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