PCI Express x16 and x8/x8 sli question

[rflorczak]

I am interested in picking up a new motherboard for gaming. I intend on getting one of the new sandy bridge chips I7 2600k or I5 2500k. I have noticed with the motherboards for these chips that the pcie details usually list 2.0 x16 but i have discovered that most of the boards run the slots at different speeds depending on the number of cards you install. For example the description says 1@16 2@8 4@4. I am only going to get one video card when i buy my new pc but I would like to have the option to upgrade to SLI in the future. What kind of performance loss if any would i experience from the 2 x8 slots? If it is alot of performance loss would it be worth it to get a much more expensive motherboard that has 2 x16 slots? If someone could explain what is going on with the slowdown based on occupied slots it would be greatly appreciated.

 

[serge44]

I am interested in picking up a new motherboard for gaming. I intend on getting one of the new sandy bridge chips I7 2600k or I5 2500k. I have noticed with the motherboards for these chips that the pcie details usually list 2.0 x16 but i have discovered that most of the boards run the slots at different speeds depending on the number of cards you install. For example the description says 1@16 2@8 4@4. I am only going to get one video card when i buy my new pc but I would like to have the option to upgrade to SLI in the future. What kind of performance loss if any would i experience from the 2 x8 slots? If it is alot of performance loss would it be worth it to get a much more expensive motherboard that has 2 x16 slots? If someone could explain what is going on with the slowdown based on occupied slots it would be greatly appreciated.

The topic has been covered on some other threads, but to save you some research time the short answer is that on most resolutions a 8x8 combination will perform the same as a 16x16. I believe that on resolutions over 5000x2000 or something the 8x8 started getting behind but by a one digit percent on fps, which was barely noticeable during actual gameplay.

Conclusion, if you can get a 8x8 mobo at a better price, go for it.

 

[rflorczak]

Best answer selected by rflorczak.