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MITSUBISHI ELECTRIC MOTHERBOARD DIVISION PAGE 30 OF 45
The BIOS also issues Port 80h codes that can be displayed using a suitable diagnostic card. The
codes can be used to determine the failure.
02h Verify Real Mode
03h Disable Non-Maskable Interrupt (NMI)
04h Get CPU type
06h Initialise system hardware
08h Initialise chipset with initial POST values
09h Set IN POST flag
0Ah Initialise CPU registers
0Bh Enable CPU cache
0Ch Initialise caches to initial POST values
0Eh Initialise I/ O component
0Fh Initialise the local bus IDE
10h Initialise Power Management
11h Load alternate registers with initial POST values
12h Restore CPU control word during warm boot
13h Initialise PCI Bus Mastering devices
14h Initialise keyboard controller
16h BIOS ROM checksum
17h Initialise cache before memory autosize
18h 8254 timer initialisation
1Ah 8237 DMA controller initialisation
1Ch Reset Programmable Interrupt Controller
20h Test DRAM refresh
22h Test 8742 Keyboard Controller
24h Set ES segment register to 4 GB
26h Enable A20 line
28h Autosize DRAM
29h Initialise POST Memory Manager
2Ah Clear 512 KB base RAM
2Ch RAM failure on address line
2Eh RAM failure on data bits of low byte of memory bus
2Fh Enable cache before system BIOS shadow
30h RAM failure on data bits of high byte of memory bus
32h Test CPU bus- clock frequency
33h Initialise Phoenix Dispatch Manager
34h Test CMOS RAM
35h Initialise alternate chipset registers.