SLI’s Speed Boost ‘Up To 56%’

A new technology that allows a PC to use two PCI Express graphics boards in tandem delivers the fastest graphics performance we’ve ever seen. We tested a system built with NVidia’s SLI (Scalable Link Interface) technology and saw a dramatic performance boost in newer games played at high resolutions–though older, less graphics-dependent games showed little or no benefit.

Alas, SLI isn’t something you can graft onto your current PC. You’ll need a new SLI-ready motherboard featuring NVidia’s own NForce4 PCI-Express chip set for Athlon 64. Four NVidia PCI Express graphics cards currently support SLI: the midprice $200 GeForce 6600 GT; and the high-end 6800, 6800 GT, and 6800 Ultra models, which cost between $300 and $500 apiece. In addition, Alienware makes a $6000 dual-Xeon SLI PC, and Gigabyte has been developing an SLI motherboard based on Intel’s 915 chip set. NForce boards built to work with Intel CPUs are still a few months away from readiness.

We tested a preproduction Asus A8N-SLI Deluxe motherboard with 6800 GT cards in both single and dual (SLI) configurations, using an ATI X800 board as a reference point. Older games such as Return to Castle Wolfenstein, Commanche 4, and Unreal Tournament 2004 depended less on the graphics board, and they showed little or no performance gain with SLI. In some cases, the SLI setup ran a frame or two per second slower than the system configured with the single card–most likely due to SLI overhead.

With newer GPU-centric games like Doom 3, Halo, and Far Cry, SLI showed a noticeable but inconsequential improvement in frame rate at 1024 by 728 resolution. When we expanded the pixel grid to 1600 by 1200, however, SLI strutted its stuff–offering gains of up to 56 percent over the single-card setup with antialiasing enabled.

PC World
Superfast Graphics
Tests of SLI technology reveal that two graphics boards really are better than one