Appendix B: Post Codes - Gigabyte GA-486AM User Manual

GA-486AM
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APPENDIX B: POST CODES

F
ISA POST codes are typically output to port address 80h.
POST Name
C0 Turn Off Chipset Cache
1 Processor Test 1
2 Processor Test 2
3 Initialize Chips
4 Test Memory Refresh
Toggle
5 Blank video, Initialize
keyboard
6 Reserved
7 Test CMOS Interface
and Battery Status
BE Chipset Default
Initialization
C1 Memory presence test
C5 Early Shadow
C6 Cache presence test
8 Setup low memory
9 Early Cache
Initialization
A Setup Interrupt Vector
Table
B Test CMOS RAM
Checksum
C Initialize keyboard
D Initialize Video Interface
E Test Video Memory
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Description
OEM Specific-Cache control.
Processor Status (1 FLAGS) Verification.
Test the following processor status flags
carry, zero, sign, overflow,
The BIOS will set each of these flags, verify they are set,
then turn each flag off and verify it is off.
Read/Write/Verify all CPU registers except SS, SP, and
BP with data pattern FF and 00.
Disable NMI, PIE, AIE, UEI, SQWV.
Disable video, parity checking, DMA.
Reset math coprocessor.
Clear all page registers, CMOS shutdown byte.
Initialize timer 0, 1, and 2, including set EISA timer to a
known state.
Initialize DMA controllers 0 and 1.
Initialize interrupt controllers 0 and 1.
Initialize EISA extended registers.
RAM must be periodically refreshed in order to keep the
memory from decaying. This function assures that the
memory refresh function is working properly.
Keyboard controller initialization.
Verifies CMOS is working correctly, detects bad battery.
Program chipset registers with power on BIOS defaults.
OEM Specific-Test to size on-board memory.
OEM Specific-Early Shadow enable for fast boot.
External cache size detection.
Early chip set initialization.
Memory presence test.
OEM chip set routines.
Clear low 64 K of memory.
Test first 64 K memory.
Cyrix CPU initialization.
Cache initialization.
Initialize first 120 interrupt vectors with SPURIOUS_INT-
HDLR and initialize INT 00h-1Fh according to INT_TBL.
Test CMOS RAM Checksum, if bad, or insert key pressed,
load defaults.
Detect type of keyboard controller (optional).
Set NUM_LOCK status.
Detect CPU clock.
Read CMOS location 14h to find out type of video in use.
Detect and Initialize Video Adapter.
Test video memory, write sign-on message to screen.
Setup shadow RAM - Enable shadow according to Setup.
B-1