>> [Such a driver would presumably have to prevent simultaneous access to the
>> card for graphics purposes or we would have some funky displays whilst the
>> machine hosed itself.]
>>
>> And a subsidary question: given a), is this idea insufficiently ambitious
>> and could/should such RAM be usable as real system memory, not just fast
>> swap?
>
> It probably can't even be used as fast swap. I suggested such an
>idea in the old GGI FAQ, and someone later told me that the VRAM+memory
>controller logic on standard video cards is designed around the assumption
>that writing to video memory will happen much, much more often than reading
>from video memory. I don't remember the particulars, but the upshot is that
>bandwith reading from VRAM is maybe 1/4 of bandwidth writing to VRAM. As
>such, VRAM reads will be so much slower than VRAM writes that any gains you
>might have gotten from the extra RAM evaporate. If you have "normal" VRAM
>I/O and maybe accels and DMA too (i.e. something is actually using the video
>card for its intended purpose) going on simultaneously the situation gets
>even worse.
Are you saying that swap to VRAM would be slower than swap to
hard disk? If that is the case, I want a video card with a hard
disk instead of video memory. ;o)
-- Mike A. Harris - Computer Consultant - Linux advocateLinux software galore: http://freshmeat.net
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