An Israeli company claims to have developed a technique (dubbed "Hydra") to run any two GPU's simultaneously (despite make or model) with improved scaling.

It is essentially a system-on-a-chip (SoC) which uses exclusive software to detect and balance the workload of multiple GPUs/graphics cards found in the system; regardless of the CPU or motherboard chipset.

It's been confirmed that the Hydra engine does not require any modification of existing software and is fully compatible with DirectX, though there is no mention of OpenGL support just yet. Providing development continues at its current pace, Lucid Logix plans to bring this technology to market as early as Q1'09. Exciting stuff; let's hope it delivers and shows performance scaling on par or better than what we're used to seeing.