| Appendix B: BIOS POST Checkpoint Codes |
|
|
Checkpoint | Code Description |
48h | Patterns written in base memory. Determining the amount of memory |
| below 1 MB next. |
49h | The amount of memory below 1 MB has been found and verified. |
| Determining the amount of memory above 1 MB memory next. |
4Bh | The amount of memory above 1 MB has been found and verified. |
| Checking for a soft reset and clearing the memory below 1 MB for |
| the soft reset next. If this is a power on situation, going to checkpoint |
| 4Eh next. |
4Ch | The memory below 1 MB has been cleared via a soft reset. Clearing |
| the memory above 1 MB next. |
4Dh | The memory above 1 MB has been cleared via a soft reset. Saving |
| the memory size next. Going to checkpoint 52h next. |
4Eh | The memory test started, but not as the result of a soft reset. |
| Displaying the first 64 KB memory size next. |
4Fh | The memory size display has started. The display is updated during |
| the memory test. Performing the sequential and random memory test |
| next. |
50h | The memory below 1 MB has been tested and initialized. Adjusting |
| the displayed memory size for relocation and shadowing next. |
51h | The memory size display was adjusted for relocation and shadow- |
| ing. |
| Testing the memory above 1 MB next. |
52h | The memory above 1 MB has been tested and initialized. Saving |
| the memory size information next. |
53h | The memory size information and the CPU registers are saved. |
| Entering real mode next. |
54h | Shutdown was successful. The CPU is in real mode. Disabling the |
| Gate A20 line, parity, and the NMI next. |
57h | The A20 address line, parity, and the NMI are disabled. Adjusting |
| the memory size depending on relocation and shadowing next. |
58h | The memory size was adjusted for relocation and shadowing. |
| Clearing the Hit <DEL> message next. |
59h | The Hit <DEL> message is cleared. The <WAIT...> message is |
| displayed. Starting the DMA and interrupt controller test next. |