Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

From: David P. Reed
Date: Mon Dec 17 2007 - 15:10:11 EST


H. Peter Anvin wrote:
Rene Herman wrote:

I do not know how universal that is, but _reading_ port 0xf0 might in fact be sensible then? And should even work on a 386/387 pair? (I have a 386/387 in fact, although I'd need to dig it up).


No. Someone might have used 0xf0 as a readonly port for other uses.

As support: port 80 on the reporter's (my) HP dv9000z laptop clearly responds to reads differently than "unused" ports. In particular, an inb takes 1/2 the elapsed time compared to a read to "known" unused port 0xed - 792 tsc ticks for port 80 compared to about 1450 tsc ticks for port 0xed and other unused ports (tsc at 800 MHz).

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