PCIE 3.0 x16 + PCIE 2.0 x4

[Jonwil]

I was thinking about getting a crossfire set up on my gigabye Z77 LGA 1155 however i noticed that one of the slots was PCIE 3.0 X16 and the other PCIE 2.0 The graphics card i currently have is an MSI Radeon HD 7950 and i was thinking about getting a crossfire setup with a Radeon HD 7970. Would the fact that these slots are x16/x4 affect anything? would i get better performance at all? Would i be even better off taking my 7950 out of the x16 and putting the 7970 there and putting the 7950 in the x4 slot?

 

[Jonwil]

I should add that i have an i5 3570k clocked at 3.4ghz so would this bottleneck the crossfire? would t still bottleneck if overclocked to 4.4ghz?

 

[spawnkiller]

You'll have some performance drop, however it's really not noticeable in real-life (only in benchmarks)

http://www.xtremesystems.org/forums/showthread.php?254239-PCI-e-x16-x8-and-x4-tests