Better performance in pci-e x8 slot.

[LaSmirk]

Hello, I recently purchased and installed a new GPU, the radeon HD 7870 (XFX edition).
My motherboard has two pci-e slots, one that runs in x16 with a single gpu, and one that runs in x8 with a single gpu.
I've been switching the card between these ports and have noticed better performance when the card is in the x8 slot than the other one. Why is this? Do I have a defective port?
Thoughts?
I've run the metro 2033 benchmark, gotten better average fps, and run 3dmark 11 and gotten a higher score, and it makes no sense to me.

 

[freneefrence]

There is no noticeable difference when running a graphic card on either pci-e x16 or x8. Otherwise there should be a problem. Try it on a different motherboard and see the results