Today I was wondering why I had 2 identical GPU's and one of them seemed to be twice as fast as the other. Many of you already know this, but apparently the PCIe Generation makes a big difference with GPUGRID.

Gen 1: 2.5 GT/s maximum link speed
Gen 2: 5.0 GT/s maximum link speed

Link speed seems to be the bottleneck at GPUGRID for my GTX 460's

The card on the Gen1 bus takes 2x the card on the Gen2 bus to complete a task.