PCI-E x16 and x16 (x4) question.


I just built a computer and I'm having an issue with the motherboard/videocard, it's a Biostar TZ77A, I have an Intel i5 2500k processor, 8gb of DDR3 Ram, Nvidia GTX460, cheap 250gb hard drive and DVD-RW drive.

The motherboard has dual PCI-E slots for Crossfire, the first slot is rated at x16 and the second is x16 (x4). For some reason the first slot (PCI-E 3.0) will not work with my videocard, I get 8 beeps and I've tried changing lots of settings in the bios with no success (the slot did work with an old ATI Radeon card i had lying around). Luckily the second PCI-E slot works with my GTX460, now to my question.

I'm being forced to use the second PCI-E slot which has a rating of x16 (x4) when run in Crossfire mode with another videocard in the first slot. If the second PCI-E slot is being used alone, does it run at x16? I think I heard somewhere in the past that the two PCI-E slots will only run x16 and x4 if they are both occupied. I ran a videogame and it seemed to have a good FPS, but I just want to verify. Thank you.
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  1. Even if it was x4, it wouldn't hinder your performance on a GTX 460.

    It barely hurts a GTX 680. With that said, the performance hinderance (and bandwith saturation) comes into play when you are running CF and SLI, that is when you need the large bandwith.

    With all that said, you are probably running at least x8, it should tell you in your motherboard manual (every motherboard manual I've seen in the last 5 years has a PCI-e layout and tells you what and when they run at different speeds).

    Also it is worth noting that in either slot, (even though the first is PCI-e 3.0 compliant) both with your CPU will only be PCI-e 2.0, because only the Ivy Bridge chips have the instructions for PCI-e3.0.

    EDIT - Found the manual for your motherboard on Biostars website, seems like it runs at x16. So yeah you should be fine.
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