Note: The memory clock of a reference GeForce 6600 GT PCI-Express is 1000 MHz, whereas it is 900 MHz on the AGP version. Keep this in mind when reading the gaming result graphs.
Comanche 4
Soltek's K890Pro-939 and Gigabyte's K8NXP-SLI are in the lead here, with a difference of 0.25 FPS between them. Soltek's AGP-based K8TPro-939 is behind a measly 2 FPS. This benchmark is highly CPU-dependant and places an emphasis on geometry throughput.
Doom 3
The Soltek K890Pro-939 clearly takes the lead here, beating its nForce4 rival by ~4 FPS. The AGP-based Soltek board takes last place, but only ~3 FPS behind the Gigabyte board. This is a 7% gap between first and last place so the performance difference is not insignificant although this may be attributed to the slight differences between the 6600GT AGP and the PCIe version