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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 |
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| C0 | Turn Off Chipset | OEM |
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| And CPU test | Processor Status (1FLAGS) Verification. | ||
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| Tests the following processor status | ||
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| flags: Carry, zero, sign, overflow, | ||
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| The BIOS sets each flag, verifies | ||
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| They are set, then turns each flag | ||
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| off and verifies it is off. | ||
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| Read/Write/Verify all CPU registers | ||
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| except SS, SP, and BP with data | ||
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| pattern FF and 00. | ||
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| RAM must be periodically refreshed to | ||
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| keep the memory from decaying. This | ||
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| function ensures that the memory | ||
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| refresh function is working properly. | ||
| C1 | Memory Presence | First block memory detect |
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| OEM | ||
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| memory. Early chip set initialization | ||
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| Memory presence test | ||
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| OEM chip set routines | ||
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| Clear low 64K of memory | ||
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| Test first 64K memory. | ||
| C2 | Early Memory | OEM Specific- Board Initialization |
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| Initialization |
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| C3 | Extend Memory DRAM | OEM Specific- Turn on extended memory |
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| select | Initialization | ||
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| Cyrix CPU initialization | ||
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| Cache initialization | ||
| C4 | Special Display | OEM Specific- Display/Video Switch |
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| Handling | Handling so that Switch Handling display | ||
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| switch errors never occurs | ||
| C5 | Early Shadow | OEM specific- Early shadow enable for |
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| fast boot | ||
| C6 | Cache presence test | External cache size detection |
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| CF | CMOS Check | CMOS checkup |
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| B0 | Spurious | If interrupt occurs in protected |
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| mode. | ||
| B1 | Unclaimed NMI | If unmasked NMI occurs, display |
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| Press F1 to disable NMI, F2 reboot. | ||
| BF | Program Chip Set | To program chipset from defaults values |
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| Setup Pages | E1- Page 1, E2 - Page 2, etc. |
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| 1 | Force load Default | Chipset defaults program |
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| to chipset |
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| 2 | Reserved |
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| 3 | Early Superio Init | Early Initialized the super IO |
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| Code(hex) | Name | Description |
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| 4 | Reserved |
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| 5 | Blank video | Reset Video controller |
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| 6 | Reserved |
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| 7 | Init KBC | Keyboard controller init |
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| 8 | KB test | Test the Keyboard |
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| 9 | Reserved |
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| A | Mouse Init | Initialized the mouse |
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| 51 |
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