BIOS POST Codes - Page 3 of 6


Code LED Display Description
40h Preparing the virtual mode test. Verify from display memory next.
41h Returned to POST after verifying from display memory. Preparing the descriptor tables next.
42h The descriptor tables have been prepared. Entering virtual mode for the memory test next.
43h Entered virtual mode. Enabling interrupts for diagnostics mode next.
44h Interrupts are enabled if the diagnostics switch is on. Initializing data to check the memory wraparound at 0:0h next.
45h Data has been initialized for the memory wraparound check. Checking for memory wraparound at 0:0h and finding the total system memory size next.
46h The memory wraparound test has been done. The memory size calculation has been done. About to write memory test patterns.
47h The memory test patterns were written to extended memory. Writing patterns in conventional memory (first 640 KB) next.
48h The patterns to be tested were written to conventional memory. Finding the amount of memory below 1 MB next.
49h The amount of memory below 1 MB was found and verified. Finding the amount of memory above 1 MB next.
4Ah The amount of memory above 1 MB was found and verified. Performing the BIOS ROM data area check test next.
4Bh The BIOS ROM data area check is done. Checking the Del key status and clearing the memory below 1 MB for a soft reset 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. Clearing the memory size next.
4Eh The memory test has started. No soft reset was performed. About to display the first 64 KB memory test.
4Fh The memory size display has started. This display is updated during the memory test. Running the sequential and random memory test.
50h The test of memory below 1 MB completed. Adjusting the memory size for relocation and shadowing next.
51h The memory size has been adjusted for memory relocation above 1 MB and shadowing options. The test of memory above 1 MB is next.
52h The test of memory above 1 MB has completed. Preparing for real mode next.
53h The CPU registers have been saved, including the memory size. Entering real mode next.
54h Shutdown was successful and the CPU is in real mode. Restoring the registers saved during preparation for shutdown next.
55h The registers have been restored. Disabling the Gate A20 address line next.
56h The Gate A20 address line was disabled successfully. Checking the BIOS ROM data area next.
57h The BIOS ROM data area check is partially completed. Completing the BIOS ROM data area check next.
58h The BIOS ROM data area check has completed. Clearing the OHit DelO message next.
59h The "Hit Del" message has been cleared. About to start the DMA and interrupt controller tests.
 

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