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Appendix D: BIOS POST Checkpoint Codes
186
09h Set in-POST flag in CMOS that indicates we
are in POST. If this bit is not cleared by post-
ClearBootFlagJ (AEh), the BIOS on next boot
determines that the current configuration
caused POST to fail and uses default values
for configuration.
Clear the CMOS diagnostic byte (register E).
Check the real-time clock and verify the bat-
tery has not lost power. Checksum the
CMOS and verify it has not been corrupted.
0Ah Initialize CPU registers.
0Bh Enable CPU cache. Set bits in CMOS related
to cache.
0Ch Set the initial POST values of the cache reg-
isters if not integrated into the chipset.
0Eh Set the initial POST values of registers in the
integrated I/O chip.
0Fh Enable the local bus IDE as primary or sec-
ondary depending on other drives detected.
10h Initialize power management.
11h General dispatcher for alternate register ini-
tialization.
Set initial POST values for other hardware
devices defined in the register tables.
12h Restore the contents of the CPU control
word whenever the CPU is reset.
13h Early reset of PCI devices required to disable
bus master. Assumes the presence of a stack
and running from decompressed shadow
memory.
Checkpoint
Code
Beep Code Description