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Do GPUs need 16x?

altich88

altich88

altich88

Associate
Joined
28 Oct 2008
Posts
233
Hi Guys,
Bit confused about this - I'm after a new mobo for my i5 and 4890, but am a bit unsure to what speed PCI slots I need. Most mobos seem to have 16x wired at 16x for the top slot, and 16x wired at 8x for the lower. Would you lose any peformance running the card in the lower slot at 8x?
It's just my CPU heatsink is rather large and would prefer to install the gpu lower if possible.
My old mobo with a GPU in the 16x wired at 4x was certainly slower :/.
Cheers
 
ive just looked into this for myself and there really is nothing in it performance wise, maybe a couple of fps, but nothing thats gonna make you see any significant difference.
ive just xfired 2 5870's both in 8x with no issues what so ever
i think someone started a thread asking the same thing last week,
anyway look here for the opinion on techpowerup http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/26.html

i know its for 5870 but im sure the same applies
 
Generally there's less than 5% difference when running a gpu on 8x or 16x.

GPUs do however take a performance hit at 4x.
 
If its x8 PCI-e 2.0 then anything upto a 5870 will be fine - might lose the odd fps off the top and marginally longer load times but thats it. If your putting something like a 5970 into an x8 slot tho you will see bigger drops.
 
i am thinking of getting hd4890's in crossfire, but just bought a new mobo with a 16x slot and a 4x slot, would it be a silly thing to do to have 1 in the 4x and 1 in the 16x??
 
Marine-RX179 said:
Graphic card won't even run properly on 4 lanes...
Click to expand...

Actually it will. Works just fine with a 16x/4x slot combo (even when the 4x slot is pci express gen 1 like in the cheaper i5 mobos). There is a performance penalty (I notices 15-20% with 5770 crossfire) but it still works.
 
I've noticed the 5*** series are PCI 2.1, slightly ahead of the 2.0

Does this make any difference? Do you need the newer mobo's to take advantage of full performance, or is there little or nothing in it.
 
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