[coreboot] PIC, APIC, XAPIC and XIOAPIC

[Rudolf Marek]

Feng, Libo wrote:
> 
> Yes. I think that after power on, IOAPIC works on PIC mode or virtual wire
> mode by default. But no device use interrupts in both coreboot and FILO,
> keyboard, vga, serial port all polling. I check the mptable.c, some people
> set the IOAPIC in PIC mode via c00h/c01h, now that no device uses it, why
> they set it? Maybe at the very beginning of OS, PIC mode is applied before
> IOAPIC is enabled. My understanding is correct or not? Thank you.

Yes its true, there is short period of time where PIC is used. So it is later 
switched to APIC.

Thanks,
Rudolf