Performance in Synthetic Benchmarks
The Sapphire Toxic HD 4850 scores only 90 points more than the reference card just as we could expect considering that the benchmark runs at 1280x1024 without FSAA by default. The SM2.0 tests show a total lack of any performance growth.
The individual SM2.0 tests confirm the point. Despite the use of 4x FSAA, there is but a small difference between the two versions of Radeon HD 4850. It fits into the measurement error range even.
The gap is somewhat larger in the SM3.0/HDR tests and you cannot write it off to some inaccuracies of the benchmarking mechanism. Anyway, the gap is no larger than 5% even here.