In Cinebench 11.5 X64 test, the rendering test does take advantage of the extra bandwidth. The score jumped from 9.22 points to 9.69 , giving a 4.99% gain in performance. In the OpenGL test, the score went from 72.52 fps to 72.79 fps.
What about 3D benchmarks then ? The difference is more noticeable with DDR3-2400 scoring 9857 and DDR3-2133 scoring 9750 giving a gain of 1.1%.
In 3DMark11, the score difference isn’t that noticeable. The difference is only 3 points away.