Technical data

Troubleshooting
4-37
DIGITAL PC 3500/5510
POST Execution Messages
During bootup, the BIOS carries out a POST routine which checks the computer
functions. While only a few execution messages display at the bottom of the screen,
the following tests are performed. If BIOS detects an error, the associated code will
be sent to port 80h. If the computer hangs before the BIOS can process the error,
the value displayed at port 80h is the last test performed.
Code Description
02h Verify Real Mode
04h Get CPU type
06h Initialize system hardware
08h Initialize chipset registers to their 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
0Fh Initialize local bus IDE
10h Initialize Power Management
11h Load alternate registers with initial POST value
12h Restore CPU control word during warm boot
13h Reset PCI bus master
14h Initialize keyboard controller
16h ROM BIOS checksum
17h Initialize external cache before RAM autosize
18h 8254 timer initialization
1Ah 8237 DMA controller initialization
1Ch Reset Programmable Interrupt Controller
20h Test DRAM refresh
22h Test 8742 Keyboard Controller
24h Set segment-register addressibility to 4 GB
continued