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APPENDIX
Debug Port Post Code
Normal POST Codes
NOTE: EISA POST codes are typically output to port address 300h.
ISA POST codes are output to port address 80h.
Code(hex) Name Description
C0 Turn Off Chipset
And CPU test
OEM Specific-Cache control cache
Processor Status (1FLAGS) Verification.
Tests the following processor status
flags: Carry, zero, sign, overflow,
The BIOS sets each flag, verifies
They are set, then turns each flag
off and verifies it is off.
Read/Write/Verify all CPU registers
except SS, SP, and BP with data
pattern FF and 00.
RAM must be periodically refreshed to
keep the memory from decaying. This
function ensures that the memory
refresh function is working properly.
C1 Memory Presence First block memory detect
OEM Specific-Test to size on-board
memory. Early chip set initialization
Memory presence test
OEM chip set routines
Clear low 64K of memory
Test first 64K memory.
C2 Early Memory
Initialization
OEM Specific- Board Initialization
C3 Extend Memory DRAM
select
OEM Specific- Turn on extended memory
Initialization
Cyrix CPU initialization
Cache initialization
C4 Special Display
Handling
OEM Specific- Display/Video Switch
Handling so that Switch Handling display
switch errors never occurs
C5 Early Shadow OEM specific- Early shadow enable for
fast boot
C6 Cache presence test External cache size detection
CF CMOS Check CMOS checkup
B0 Spurious If interrupt occurs in protected
mode.
B1 Unclaimed NMI If unmasked NMI occurs, display
Press F1 to disable NMI, F2 reboot.
BF Program Chip Set To program chipset from defaults values
E1-EF Setup Pages E1- Page 1, E2 - Page 2, etc.
1 Force load Default
to chipset
Chipset defaults program
2 Reserved
3 Early Superio Init Early Initialized the super IO
Code(hex) Name Description
4 Reserved
5 Blank video Reset Video controller
6 Reserved
7 Init KBC Keyboard controller init
8 KB test Test the Keyboard
9 Reserved
A Mouse Init Initialized the mouse