It's strange, but you are not the only one to notice it. We talked about it a bunch on the 670 Hands On thread over the past few days.
For your 680, tests 1, 2, and 4 are slightly faster in centered mode, but test 3 is WAY faster in stretched mode ... the extra FPS from test 3 more than makes up for the loss in the other 3 in stretched mode, and increases your GPU score by 500.
My cards don't do this (I don't think) but if I decide to not be lazy I'll let you know my results.
A forum community dedicated to overclocking enthusiasts and testing the limits of computing. Come join the discussion about computing, builds, collections, displays, models, styles, scales, specifications, reviews, accessories, classifieds, and more!