About copying memory

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Original post by Anonymous Poster
system-to-system should always be faster than system-to-video or video-to-system, since there is no slow PCI or AGP bus in the middle.

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AGP isn''t a bus, it''s a port (it only permits communication between two devices; the processor/chipset, and the video processor), and AGP isn''t particularly slow. AGP 4x offers a theoretical 1000-odd MB/sec transfer rate (PC100 memory offering 800 MiB).

It doesn''t seem entirely unreasonable that an architecture can experience faster transfers from system RAM to video card than it can from system RAM to system RAM; in principle, it should be able to just blast the data out of system memory into video processor; copying from system memory to system memory requires both reads and writes, which should be contending for the same bus.