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SubjectRe: IO delay, port 0x80, and BIOS POST codes
Date
Followup to:  <a6qtb8$6fg$1@penguin.transmeta.com>
By author: torvalds@transmeta.com (Linus Torvalds)
In newsgroup: linux.dev.kernel
>
> I suspect the _real_ solution is to stop using "inb_p/outb_p" and make
> the delay explicit, although it may be that some drivers depend on the
> fact that not only is the "outb $0x80" a delay, it also tends to act as
> a posting barrier.
>

... as well as a push-out to the ISA bus. I suspect dumping the outb
way of doing it and instead wait in the CPU might cause the delay to
happen in the wrong part of the system (consider split-transaction
queued busses like HyperTransport, where a delay in the CPU doesn't
necessarily mean a delay in the southbridge.)

Port 0x80 has served us well, at least as a default. If you really
care about the POST display you can recompile using a different port.

-hpa
--
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com>
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