An interesting chart that we created may explain the huge disparity between the GTX 680 and HD 7970 in minimum FPS and we believe it has everything to do with onboard RAM. Looking at the graph we've made, you can see that the two cards basically use about the same amount of RAM on the high preset, but the difference is much wider in the ultra preset. In the high preset, the GTX 680 uses 1436 MB while the HD 7970 uses 1471, a negligible difference, but a difference nonetheless. With the ultra preset, however, we noticed two things. The HD 7970 uses 2342 MB while the GTX 680 uses 2043 MB, which would normally lead one to say that the HD 7970 is purely a more memory hungry graphics card. But there is one factor many will overlook. The GTX 680 has 2048 MB of installed RAM while the HD 7970 has 3072 MB of RAM, which means the GTX 680 basically exhausted all GDDR memory when trying to run Battlefield 3 in 4K at ultra settings.
Minnesbandbredden är för låg för att nyttja 4gb. Och dom testade inte högsta möjliga inställningar.