Thread: PCI 2.0 x16 slot speed question    

With motherboards that have x16; x16/x16 / x16/x8/x8 support, does that mean pci slot 1 will have x16, 2 will have x16 or x8 and 3 can only have x8? I ask because I am looking into running 2 480s on a rampage III. I want to set them up in slot 1 and 3 so they can run cooler but I don't want the other card running at x8 instead of x16. Thanks.

I assume you're talking about Extreme and not Gene? As Gene only has 2 PCI slots, however Extreme has 4 so... Anyway, the x16/x16 means that in normal SLI, both of your cards will run at x16 if they're both in PCI Express 2.0 x16 slots. x16/x8/x8 for example only takes effect in TriSLI and means that one card will run at x16 and the other 2 will run at x8, not that slot one will run at x16 and slot 2 and 3 will run at x8 (even though that is likely how the lanes will be distributed). That seems to be what you were asking, if not then I misunderstood.

tl;dr - x16/x16 denotes how fast your cards will run in dual-GPU SLI, not that slot 1 and 2 will run at x16/x16 specifically and that slot 3 and 4 can't.

Thank you. That is what I was asking.

Originally Posted by Knyghtmayre

I assume you're talking about Extreme and not Gene? As Gene only has 2 PCI slots, however Extreme has 4 so... Anyway, the x16/x16 means that in normal SLI, both of your cards will run at x16 if they're both in PCI Express 2.0 x16 slots. x16/x8/x8 for example only takes effect in TriSLI and means that one card will run at x16 and the other 2 will run at x8, not that slot one will run at x16 and slot 2 and 3 will run at x8 (even though that is likely how the lanes will be distributed). That seems to be what you were asking, if not then I misunderstood.

tl;dr - x16/x16 denotes how fast your cards will run in dual-GPU SLI, not that slot 1 and 2 will run at x16/x16 specifically and that slot 3 and 4 can't.

In having 3 cards SLI'd, but 2 running at x8, wouldn't that cause the 1st card to run slower (on the x16 bus)? I don't know much about multiple GPU setups but I thought they all ran at the same speed.