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190
Checkpoint
Beep Code
Code
49h
4Ah
4Bh
4Ch
4Eh
4Fh
50h
51h
52h
54h
55h
Appendix D: BIOS POST Checkpoint Codes
Description
Perform these tasks:
1. Size the PCI bus topology and set bridge
bus numbers
2. Set the system max bus number
3. Write a 0 to the command register of
every PCI device
4. Write a 0 to all 6 base registers in every
PCI device
5. Write a -1 to the status register of every
PCI device
6. Find all IOPs and initialize them.
Initialize all video adapters in system.
Initialize QuietBoot if it is installed. Enable
both keyboard and timer interrupts (IRQ0
and IRQ1). If your POST tasks require inter-
rupts off, preserve them with a PUSHF and
CLI at the beginning and a POPF at the end.
If you change the PIC, preserve the existing
bits.
Shadow video BIOS ROM if specified by
Setup, and CMOS is valid and the previous
boot was OK.
Display copyright notice.
Initialize MultiBoot. Allocate memory for
old and new MultiBoot history tables.
Display CPU type and speed.
Checksum CMOS and initialize each EISA
slot with data from the initialization data
block.
Verify keyboard reset.
Initialize keystroke clicker if not enabled in
Setup.
Enable USB devices.
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