Re: Linux Post codes during runtime, possibly OT

Jamie Lokier
2001-01-28T17:23:54Z

H. Peter Anvin wrote:
> It is; you'd have to specify "eax" as a clobber value, and that is
> undesirable.

For outb_p, EAX is used, usually for the last time, in the preceding
"out" instruction so clobbering it is not a big deal.

For inb_p, you first have to copy EAX to another register before
outputting the post_byte. That's a small penalty. Are in[bwl]_p used
anywhere time critical? (Richard Johnson's explanation for outb_p
implies that inb_p is not required, but perhaps that explanation doesn't
tell the whole story).

> And you're still overwriting the POST value written by the BIOS.

Can the BIOS-written value be read from port 0x80?

-- Jamie