The 758 the first slot is 16X all the time, the 2nd 16X as long as the third is empty and 8X if anything is in the third. The Only way to get 2(16X ) performance is the top two full PCIe slots ocupied. http://www.youtube.com/watch?v=rSfifE2Domo

turok_t

I have an EVGA X58 3X SLI motherboard (132-BL-E758-A1) and two 6950 in crossfire. Can I use the first and third PCIe slots for my setup? Or does it have to be the first two slots? The reason why im asking is because i have aftermarket coolers on each one and I want to maximze the air circulation between them. Thanks

EDIT: If i use slot 1 and 3 versus slot 1 and 2, will it be slower?

 
You can run in either slot. However, as was pointed out, if you run in the bottom PCIe 2.0 slot the card will run at x8 instead of x16. At worst you might see a 1 or 2% decrease in benchmarks.

turok_t

Thanks for all the tips. I was flipping through the manual and it says this:

"When using 2 Graphic Cards in PCI-E Slots 1 and 3, a speed of x16/x16 will be used."

So how come you guys said that it will run at 8x if i put the second card in the bottom (third) slot? Am i missing something?

Because with the E758 X58 board only the top slot is always x16 link width. If you populate the bottom slot, the middle slot will drop to x8 link width. You're either reading the manual wrong or it is a misprint in the manual. Because if you look at the middle slot on the motherboard it will say right under it "PCIE_X16/X8_2" This means that the slot is capable of x16 link width but will drop to x8 if the bottom slot is used. Now if you look at the bottom slot you'll see "PCIE_X8_3" this tells you that the slot is only capable of x8 at most.
 
But as has been said, it really isn't going to impact your performance in any noticeable way if you're running 1 card at x8 link width.

Ahh! I thought so.. I think the manual was just printed wrong as can be seen above.. not sure why it said x16/x16.. but im sure what it really means its x16/x8...

turok_t

i know that this question may be out of the blue, but i have two 6950 flashed to 6970. Currently, Im using a core i7 920 @ 3.0Ghz with an EVGA 3x SLI mobo. Do you think my cpu is bottling down my video cars? Thanks

Yes, at only 3Ghz you can certainly clock your CPU more to gain performance on your GPUs.

The temp that the down clock and or shut down, ( called TJ max is around 100, but may be slightly deferent for each chip ) the temp most use to make sure they never see 100, is 85. ( giving you a 15 safety net ) these temps are measured during stress test with programs like LinX IBT, or prime 95. The voltages that Intel warns against is 1.4 for Vcore and Vtt, and 1.65 for DimmV; but, if your cooling is up to the task, you can exceed the voltages, just never admit it to Intel, infact never admit Overclocking at all.