Jos Hulzink <[EMAIL PROTECTED]> writes:
> On 2 Nov 1999, Marcus Sundberg wrote:
>
> > Basicly you never want to cache anything that sits on the other side
> > of the PCI-bus. MTRR write combining should always be turned on for
> > memory, but never for registers. That's about it.
> > AGP is ofcourse another story...
>
> Eh.. Enabling MTRR write combining for the videomemory of some chips
> causes crashes. Yes it's me again with my outdated ViRGE :)
Why am I not surprised... ;)
But that's just one flag passed from the driver to the OS-layer,
telling it that it shouldn't do any sort of burst accesses to video
memory. (I'm assuming that's what causes trouble with write combining).
> And I like to know your AGP story, for it seems S3 has managed to get a
> ViRGE listening to an AGP bus... (AGP0.0001X or something...)
Well, my AGP story is that I don't know much about it. ;)
But for the CPU accessing the AGP card AFAIK there's no difference
compared to PCI, except mayby the speed. If I have understood things
correctly the real difference is that an AGP card can access main RAM
in a really fast way.
//Marcus
--
-------------------------------+------------------------------------
Marcus Sundberg | http://www.stacken.kth.se/~mackan
Royal Institute of Technology | Phone: +46 707 295404
Stockholm, Sweden | E-Mail: [EMAIL PROTECTED]
