Okay. So, that article shows that bench with NO AA, and the one I linked, with 355% improvement in frames on the 1G version, shows it WITH 4xAA.
But even IN the graph YOU are linking to, at 2560x1600, we see:
8800GT 1024MB = 26 FPS
8800GT 512MB = 10 FPS
I'm still waiting for someone to explain to me HOW the 1G card can OUTPERFORM the 512MB card by between 40% and 355% on ANY benchmarks (let alone on 4 different games) *IF* it is in fact the case that the 256bit memory bus, somehow, by it's very NATURE, renders the extra 512MB of memory USELESS, which is what has been argued by a couple of other posters.
If someone wants proffer this idea that VRAM (amount in megabytes) > 2 x Bus Width (measured in bits) is a waste, that's fine. As VERY GENERAL rule, I would tend to agree.
But what I DO NOT agree with (and in fact know to be wrong), is that it's actually 'that simple', or that there are any absolutes involved here.
The equation you suggest is NOT based on any sort of 'real math' ... it's a borderline arbitrary, 'thumb in the air' GUESS. Nothing more.
There's a lot more to the REAL equation.
And again, for your assertion to be correct about the 8800GT not being able to make use of the extra 512MB, there would have to exist no benchmarks that refute your assertion. Clearly, there are such benchmarks, therefore ...