For some reason - probably to do with the way OpenGL texture caching is handled by the Nvidia's driver - Video Memory Watcher would not work with Quake 4 and gave results that were worthless. Still, the frame rate results gathered are interesting enough to include, that's for sure.

The performance margins in Quake 4 are impressive to say the least. Every test sees noticeable, real world increases in performance on the 512Mb card.

The results with 4xAA and 8xAF were largely the same as those above. The difference the extra memory appears to make is astounding. I wasn’t confident to leave my Quake 4 testing at this point as the evidence to suggest the performance increase was down to extra memory was non-existent. I decided I needed more evidence to be able to assume the extra performance was exclusively down to more memory. I went back and made sure these results were accurate and that I didn’t have something miss-configured but the results always came out the same. My first clue as to why even the 1024x768 results were very different was this warning message in Quake 4 that appears on selecting Ultra mode:

Is it stating that no matter what setting you use, regardless of having AA or AF on it is going to be using near on 500MB? Surely that’s a bit excessive, but those performance figures do suggest this is the case.

I dusted off an X1800 XT 512MB and installed it to see how Video Memory Watcher reacted to an ATI card, and sure enough it worked. It would only display card memory numbers though, for some reason it would not disclose system memory usage, but it’s better than nothing! Anyhow, as long as my tests did not use more than the 512MB of card memory they would be reasonably accurate. Here are the results:

Sure enough, memory usage is sky high in Ultra mode, even at 1024x768. This explains why the 512MB 7800 GT performs so much better in every resolution. The 256MB card cannot handle Ultra mode in any resolution, the system memory usage at 1024x768 would be around 120MB and it can only increase from there. Interestingly, high quality mode is extremely efficient. It almost looks a bit odd to see it only using 120MB total for texture memory but if you add on 4xAA and perhaps 16xAF you get closer to 200MB – a good healthy number to have for 256Mb cards. This in my opinions proves that the performance increase on the 512Mb 7800GT came from the increased VRAM.