Quake 4
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What happened with Far Cry happens with Quake 4. The 6800 standard can keep pace with the X1600 PRO by virtue of a wider memory bus, and the 7800 GS boards are a decent upgrade from everything else, performance wise. It's interesting to see 5900 Ultra match X1600 PR0 and 6800 standard here. 256-bit memory bus and 256MiB of memory definitely help.