Phoronix has tested VisionTek’s Radeon HD 4870 X2 2GB under Ubuntu 8.04.1 32-bit with the Linux 2.6.24 kernel and the latest ATI Catalyst 8.8. Catalyst 8.8 for Linux supports CrossFire, OverDrive overclocking, adaptive anti-aliasing, and other improvements. The benchmark suite used by Phoronix includes OpenGL titles like Doom 3, Quake 4, Enemy Territory: Quake Wars and the Phoronix Test Suite.
The conclusion of this test is the Radeon HD 4870 X2 isn’t quite as far as two Radeon HD 4870 512MB graphics cards linked together via CrossFire, but it’s darn close.
Read the complete test here: VisionTek Radeon HD 4870 X2 2GB.