990FXA-UD5 - Best Crossfire Slots

Craterloads · 21 May 2014 at 22:23

Hi, Just putting together a rig with 2x 290s and was wondering which slots to use on said mobo

Issue is the 1st and 3rd slots are x16 but card are practically touching, hot beasts as they are.

Was wondering if I could use the x4 or x8 slots (4 or 5) without any performance loss?

Doomedspeed · 21 May 2014 at 22:32

From gigabyte:

(Note 3) For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16_1 slot; if you are installing two PCI Express graphics cards, it is recommended that you install them in the PCIEX16_1 and PCIEX16_2 slots.

(Note 4) The PCIEX8 slot shares bandwidth with the PCIEX16_2 slot. When PCIEX8 is populated with a PCI Express expansion card, the PCIEX16_2 slot will operate at up to x8 mode.

Another clue is this:

Support for 2-Way/3-Way AMD CrossFireX™ and NVIDIA SLI™ technology

I know that SLI needs x8/x8, whereas Xfire only needs x8/x4 (x16/x4) which is why it supports Tri-fire but only SLI.

I think you'll lose performance if you use the 3rd slot, but i bet it wont be much, in the long run.

If you can it may be worth running a test.

Wilko_Dog · 21 May 2014 at 22:50

I'm having the same problem , my 2nd 270x 4gb is coming tomorrow and I'm wondering which slot to use the 2nd or 3rd.. My mobo is X58A-UD3R ... Any idea doomedspeed ?

Doomedspeed · 22 May 2014 at 07:15

Wilko_Dog said:
I'm having the same problem , my 2nd 270x 4gb is coming tomorrow and I'm wondering which slot to use the 2nd or 3rd.. My mobo is X58A-UD3R ... Any idea doomedspeed ?

Surely the second PCI-E lane is blocked by your other card, no?

Third one down would be ideal.

Wilko_Dog · 22 May 2014 at 09:37

Doomedspeed said:
Surely the second PCI-E lane is blocked by your other card, no?

Third one down would be ideal.

Ah yeah sorry .. There's 3 possible slots I could plug it into though as the mobo supports up to 3 x xfire .. So out of the 2 available , would you plug it in the one nearest the card which is already in or miss that one and plug it in one underneath ?

Craterloads · 22 May 2014 at 18:47

Tested all 3 and not much difference surprisingly

16x + 16x slots

16x + 8x slots

16x + 4x slots

Probably just going to use 16x + 4x slots as using the 8x slot blocks the USB 3.0 port!