2 posts • joined Wednesday 28th November 2007 17:34 GMT
Re: Look Ma, no main memory left!
Actually, modern cards don't map all of video ram into PCI space. Typically they only expose the first 128 or 256Mb. In practice the CPU never accesses video ram directly because it's painfully slow (very high latency). All data is transfered via the card's DMA engine.
This is ignoring the fact that even 32-bit x86 cpus have had 36-bit physical addressing for years (though not all of that is available for PCI devices), and a quad-card system is kinda dumb if you have a meaty CPU and buckets of ram to back it up.
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