Prey runs on an engine from Doom 3 , the first game to declare its use of 512 megabytes of graphics memory. However, this game seems to be quite satisfied with 256MB. The speed of the GeForce 7950 GT is limited by other factors, rather than by the amount of onboard memory, whereas the increased frequencies of the Foxconn GeForce 7950 GT 256MB in comparison with the reference card have a positive effect on performance.
Serious Sam 2
Serious Sam 2 is known to be fastidious about the amount of graphics memory on board the graphics card. This is a consequence of the design of the game engine which uses high-quality textures and shaders with multiple texture lookups. As a result, the GeForce 7950 GT 256MB is over 20% slower than the Gigabyte card in 1280x1024 resolution and about 25% slower in 1600x1200 and 1920x1200. Although the increased frequencies improve performance of the Foxconn card, the Gigabyte card with 512 megabytes of memory is anyway much faster.
Thus, the necessity of having 512 megabytes of graphics memory is obvious in this test.