Gaming and overclocking
We deliberately use graphics subsystems that allow for multi-GPU operation on a particular platform. For the two Foxconn boards (Intel P35, i975), two ASUS boards (P35, P965) we've used ATI's X1900 XTX and CrossFire cards. For the ECS nForce 680i SLI and EVGA nForce 680i LT SLI we've used a pair of GeForce 7900 GTXs. The choice of graphics cards may not allow for complete comparisons between motherboards, but, we feel, it's more a real-world indication of the kinds of GPUs that would be bought by readers who opt for a particular chipset, thereby keeping an upgrade path for multi-GPU operation open in the future.
Each of the four motherboards under the blue-coloured bars are capable of CrossFire, albeit with the P35 and P965 chipsets limited to 16+4 PCIe lane support and the i975X auto-negotiating to 8+8. NVIDIA' high-end duo offer 16 lanes per slot (16+16) for its range of SLI-capable GeForce graphics cards, and the corresponding bars are colored in green.
What we see is that CrossFire performance isn't unduly hindered by having the second card occupy a mechanical x16 slot that's only capable of signalling at x4. That's the case with X1900 XTXs, but bandwidth implications may come into play with faster cards such as the Radeon HD 2900 XT.
