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Appendix D: BIOS POST Checkpoint Codes
190
49h 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.
4Ah Initialize all video adapters in system.
4Bh 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.
4Ch Shadow video BIOS ROM if specified by
Setup, and CMOS is valid and the previous
boot was OK.
4Eh Display copyright notice.
4Fh Initialize MultiBoot. Allocate memory for
old and new MultiBoot history tables.
50h Display CPU type and speed.
51h Checksum CMOS and initialize each EISA
slot with data from the initialization data
block.
52h Verify keyboard reset.
54h Initialize keystroke clicker if not enabled in
Setup.
55h Enable USB devices.
Checkpoint
Code
Beep Code Description