We tested two Radeon HD 4850 in CrossFire running on ASRock X48TurboTwins-WiFi Intel X48 mainboard and got the following scores.
With our 9600GT Turbo which performs similarly to a 8800GT, it is no match for the single card Radeon HD 4850. 4346 vs 7155. It is 64% faster.
With CrossFire enabled using Catalyst 8.6, the result shot up to 11712. That is shocking high. The test is run on Intel QX9770 (3.2GHz) with 2GB DDR3-1600.
3DMark Vantage
Vvikoo 9600GT Turbo
4346
AMD Radeon HD 4850
7155
AMD Radeon HD 4850 (CF)
11712
