POST Code Error Messages
The following codes are not displayed on the screen. They can only be viewed on the LED display of a so called POST card. The codes are listened in the same order as the according functions are executed at PC startup. If you have access to a POST Card reader, you can watch the system perform each test by the value that's displayed. If the system hangs (if there's a problem) the last value displayed will give you a good idea where and what went wrong, or what's bad on the system board.
CODE | CHECK | DESCRIPTION OF CHECK |
C0 | Turn Off Chipset | OEM |
01 | Processor Test 1 | Processor Status (1FLAGS) Verification. Tests the |
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| following processor status flags:carry, zero, sign, |
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| overflow, The BIOS sets each flag, verifies they are |
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| set, then turns each flag off and verifies it is off. |
02 | Processor Test 2 | Read/Write/Verify all CPU registers except SS, SP, |
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| and BP with data pattern FF and 00. |
03 | Initialize Chips | Disable NMI, PIE, AIE, UEI, SQWV Disable video, |
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| parity checking, DMA Reset math coprocessor |
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| Clear all page registers, CMOS shutdown byte |
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| Initialize timer 0, 1, and 2, including set EISA timer |
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| to a known state |
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| Initialize DMA controllers 0 and 1 Initialize interrupt |
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| controllers 0 and 1 Initialize EISA extended |
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| registers. |
04 | Test Memory | RAM must be periodically refreshed to |
| Refresh Toggle | keep the memory from decaying. This function |
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| ensures that the memory refresh function is |
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| working properly. |
05 | Blank video | Keyboard controller initialization |
| Initialize keyboard |
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06 | Reserved |
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07 | Test CMOS | Verifies CMOS is working correctly, |
| Interface and | detects bad battery. |
| Battery Status |
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BE | Chipset Default | Program chipset registers with power |
| Initialization | on BIOS defaults. |
C1 | Memory presence | OEM |
| test | memory |
C5 | Early Shadow | OEM |
C6 | Cache presence | External cache size detection |
| test |
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08 | Setup low 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. |
09 | Early Cache | Cyrix CPU initialization |
| Initialization | Cache initialization |
0A | Setup Interrupt | Initialize first 120 interrupt |
| Vector Table | vectors with SPURIOUS_INT_HDLR and initialize |
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| INT |
0B | Test CMOS RAM | Test CMOS RAM Checksum, if bad, or |
| Checksum | insert key pressed, load defaults. |
0C | Initialize | Detect type of keyboard controller |
| keyboard | (optional) |
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| Set NUM_LOCK status. |
0D | Initialize Video | Detect CPU clock. |
| Interface | Read CMOS location 14h to find out type of video |
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| in use. |
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| Detect and Initialize Video Adapter. |
0E | Test Video | Test video memory, write |
| Memory | message to screen. |
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| Setup shadow RAM - Enable shadow according to |
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| Setup. |
0F | Test DMA | BIOS checksum test. |
| Controller 0 | Keyboard detect and initialization |
10Test DMA Controller 1
27 |