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SubjectRe: K6-2 MTRR Problem
Richard Gooch wrote:
>
> H. Peter Anvin writes:
> > Followup to: <199906160823.SAA04602@vindaloo.atnf.CSIRO.AU>
> > By author: Richard Gooch <rgooch@atnf.csiro.au>
> > In newsgroup: linux.dev.kernel
> > >
> > > Michael McLinn writes:
> > > >
> > > > It seems something isn't right with MTRR support for the K6-2,
> > > >
> > > > I have a K6-2 450, running 2.2.10.
> > > >
> > > > When I boot, there is a /proc/mtrr, but it is empty.
> > > >
> > > > When I
> > > > echo "base=0xe8000000 size=0x10000000 type=write-combining" >| /proc/mtrr
> > > ^^^^^^^^^^
> > >
> > > So you have 256 MiB of RAM on you graphics card? Where can I buy one?
> >
> > The standard AGP aperture is 256 MiB; doesn't mean that the card
> > actually has that much.
>
> Ah. How gross.
>
> > However, please note that the base address (0xe8000000) and the size
> > (0x10000000) are incompatible!
>
> Indeed! So the AGP spec doesn't say anything about base address
> increments? It would seem prudent for them to revise that part of the
> PCI spec too...
>

AGP uses PCI base registers to assign the base of its window.
Accordingly, the data Michael McLinn put in are simply bogus: (base &
(size-1)) must be 0.

-hpa

--
"The user's computer downloads the ActiveX code and simulates a 'Blue
Screen' crash, a generally benign event most users are familiar with
and that would not necessarily arouse suspicions."
-- Security exploit description on http://www.zks.net/p3/how.asp

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