I didn't know where to ask but i think this would be the right place regardless.

If a motherboard's pci-e lanes with a multi gpu configuration operated at say

16x/8x/8x
16x/16x/4x
16x/16x/16x/8x

I'm wondering how does the bandwidth balance itself out, would it be correct to say that your performance would drop to the lowest pci-e lane speed on all lanes regardless if its operating at 16x

example

16x/16x/4x

even though gpu-z will show that slot 1 and 2 use 16x operating system, the performance on the other hand would be 4x on all lanes.

I myself have tested a 16x/16x/16x system against a 16x/16x/4x system and the performance if i recall resulted in about 10-12 fps less in the 3dmark vantage space test, it was 3 gtx 280's with a i7 4.0ghz.

If anybody would happen to know a for fact some information in regards would be much appreciated.