Running GPU in PCI-E 16x Mechanical but 8x actual

[Kanoe]

Bit of an odd question I know but does anyone have any thoughts are how badly or not my R9 295X2 would be affected if I tried to run it from a PCI-E 2.0 16x Mechanical but in 8x mode?

I know a lot of people say that running a 280/290 at 8x isn't too bad but for a GPU that is actually 2 GPU's on one PCB I imagine it would be fairly detrimental but not sure how much so.

 

[Martini1991]

I'd be more concerned about the CPU you're running?
I think you'd get a bit of a hit with a 295 in an 8x 2.0 slot also.

 

[Kaapstad]

It depends on

The resolution you game at.

The games themselves.

What you are using the other slots for.

But to answer your question it could be as little as 4% or 5% or as much as 25% or more.

Does you mobo not have at least one slot that can run @X16.