Hi, I'm considering getting a GeForce 9800 GTX +, and my motherboard only has a PCI express x4 slot. This card is x16. I know it should work. My question is how much will it slow down being in a x4, and would I run into any problems using this card in a x4 rather that a x16? Would it be better to get a Sapphire HD 3850 AGP card? Would it be more powerful and faster? I am looking for the very best, able to run Crysis.
Get the 9800GTX+ since you can use it in your future build. It depends on the game but 4x can limit your card if it's transfering information constantly over the bus. It will depend on what game you are playing as to what the performance hit will be. By the way keep in mind that the link michaelmk86 put up referes to PCI-E 2.0 lanes. A 4x PCI-E 2.0 link has the same bandwidth as an 8x PCI-E 1.0 link. Thus if you just have a 1.0 slot you will have more of a performance hit. That being said the 9800GTX+ with a 4x 1.0 link should still generally out preform the 3850 with an AGP 8x interface.
If it's a 2.0 link, which I doubt, then the single directional bandwidth should be the same, but of course since PCI-E is bi directional it should actually prove a little better. I think you would be better off with a 4850 1GB, but if you have your hear set on the 9800GTX+ then get it and you will be able to use it with your next build while the same cannot be said for the AGP 3850. Besides, the PCI-E version of the 3850 costs half as much and should give you similar performance to the AGP version.