Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

Pavel Machek
2007-12-09T18:06:17Z

On Sat 2007-12-08 14:25:02, David P. Reed wrote:
>
>
> Alan Cox wrote:
> >
> >0x80 should be fine for anything PC compatible anyway,
> >its specifically
> >reserved as a debug port and supported for *exactly*
> >that purpose by
> >many chipsets.
> >
> >
> Disagree. The definitions of PC compatible are quite
> problematic. I have the advantage over some of you
> young guys, in that I actually wrote code on one of the
> first 5 breadboard IBM PCs on the planet at Software
> Arts, Inc. and I was directly involved in hardware spec
> projects with the original IBM and Compaq engineers. No
> one actually defined the port numbered 80h as a
> "standard" for anything. You won't find it documented
> in any early manual for an IBM machine.
>
> The ISA bus supported unterminated transactions safely.
> That allowed some clever folks to design BIOS diagnostic
> tools that optionally plugged into the bus.
>
> In any case, my machine does not have an ISA bus. Why
> should it? It's a laptop!

There are mini-pci based cards with port 0x80 displays for notebooks.

Pavel
--
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