B-5
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.
