PCIe card order

Deathjester · 22 Jul 2015 at 12:52

Hi all,

I have an Asus Rampage IV Extreme with the following:

PCI-AC68 wireless card
2x GTX Titans
1 Asus Xonar Phobeus

Since I'm running all of these does it really matter which PCIe slots I'm using?

Previously I was running just the titans and had them in 1 & 4 as recommended in the manual for x16/x16 operation however with 4 PCIe devices I assume that this will only be running at x16 / x8 (with the other 2 devices running @ x8).

Thus if I move the GPU's to 1 & 2, then use 4 & 6 for the other 2 devices this shouldn't make any discernable difference... should it?

As a side note it's a 4930k so has 40 PCI-e lanes.

Deathjester · 22 Jul 2015 at 14:31

I found this if it helps:

__________________________________________________
|_________|_______________________________________ _| - 1st port, x16 width in every case

__________________________________________________
|_________|_______________________________________ _| - 2nd, linked with 3th, x8 for both
If ^ 2nd runs in x8 mode v 3th is off!
__________________________________________________
|_________|_______________________________________ _| - 3th, linked with 2nd, x8 for both

__________________________________________________
|_________|_______________________________________ _| - 4th, can run x16, linked with 6th, x16 for both

_________________
|_________|_______| -5th, PCI-E v2.0 x1 port

__________________________________________________
|_________|_______________________________________ _| - 6th, linked with 4th, x16 for both

x16 (1st) + x8 (2nd and 3th) + x16 (4th and 6th) = 40 (CPU limit)

demonix · 22 Jul 2015 at 18:35

I might be wrong, but if there's nothing in slot 6 and the other two cards are occupying either slot 2, 3 or 5 then the two GTX Titans will still be running at 16x since slots 1 and 5 are solo and aren't linked to any other PCI-E slots on the board with 2+3 and 4+6 being linked (I'd have to guess that the sound card is in the 1x slot and the wireless card is occupying one of the other slots with 3 and 4 being the obvious suspects as to its location).

Deathjester · 23 Jul 2015 at 01:06

Using slots 1, 3, 4 & 6 my GPU in 4 is only working @ 8x.

I will try the other config as I rebuild in a week or so and feed back.

Thanks