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SubjectRe: > 1GB on alpha. Patch to 1TB?
On Sat, 13 Mar 1999, Richard Henderson wrote:

> With 32-bit PCI devices, it is difficult to get past 2GB RAM. More
> than that requires either bounce buffers or that PCI windows be
> adjusted at runtime to cope with the various outstanding DMA requests.
> Which would be cool, but i think fairly tricky to modify all the
> drivers to get right.
>
> However, there's no reason we can't support 2GB instead of 1.

While that's true Richard, it is something which is going to have to be
done and probably fairly soon.
2GB machines are not too unusual these days and that means 4GB machines
will be not unusual in a year. But 64 bit PCI cards seem to be slow in
appearing in any large numbers so we have to presume that we will get
large memory systems with 32 bit PCI devices in (even if they are just
things like graphics cards - althogh I wouldnt mind a 64bit PCI graphics
card for my Alpha....)

Similar problems afflict Linux systems running on processors on PCI
cards who want to see a reasonable section of the host memory and yet
allow their own memory to be visible to the host.

Dave
--------------------------------------------------------------------
/ Dr. David Alan Gilbert | Running Linux on | Happy \
\ gro.gilbert @ treblig.org | Alpha, ARM and SPARC | In Hex /
\____________________________|___ http://www.treblig.demon.co.uk __/


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