there is suppose to be both pcie and agp versions. pcie first I think
but remember to buy the GT version of 6600 though if you are consider buying the nvidia card.
The following is a possible comparsion of the gT and non GT version. (they lower the clock speed of the gT version for tetsing ie (300/600))
http://www.neoseeker.com/Articles/Ha...ch1/index.html