Crossfire and PCIe

[vertical777]

hi,
I want to know if how much of a performance boost will I get if I upgrade my motherboard from x16/x4 PCIe 2.0 to x8/x8 PCIe 2.0
I'm running a 5770 crossfire setup. Would there be a significant improvement in terms of frame rates, 3d rendering, etc?

 

[Helltech]

Crappy ASUS? Those words should never be in the same sentence!

I think you are plenty fine with 16x and 4x.

If you compare 2 x16 to;
a) 1 x16 and 1 x8 you won't even notice a difference.
b) 2 x8 you will see about a 5% loss.
c) 1 x16 and 1 x4 you will see like a 10-15% loss in the second card.

So if that quick research I made was accurate... You would go from 100 percent on the first card and 85~percent on the second card (x16 + x4), to 95 percent on each card (x8 + x8).

That difference is very little in my opinion.

I also found this interesting...

http://www.overclockers.com/forums/showthread.php?t=629631

Which makes it seem like even less of a difference.

 

[Maziar]

Hello
x16x4 is the worst performer in CrossFire,moving towards either dual x8 or x16 will give you a great boost in performance, here is a good(a little old,but you'll get the idea) article,which compares them all
http://www.tomshardware.com/reviews/crossfire-pci-express,2095.html

 

[vertical777]

oh, sorry bout the offensive language, yes crappy and asus must not be in the same sentence, the situation got out of hand there I'm gonna edit it out for ya

 

[Helltech]

oh, sorry bout the offensive language, yes crappy and asus must not be in the same sentence, the situation got out of hand there I'm gonna edit it out for ya

Haha, I was just kidding.

And I guess I was wrong, Maziar is far more knowlegable then myself.

 

[vertical777]

Hello
x16x4 is the worst performer in CrossFire,moving towards either dual x8 or x16 will give you a great boost in performance, here is a good(a little old,but you'll get the idea) article,which compares them all
http://www.tomshardware.com/reviews/crossfire-pci-express,2095.html

how great is "great" really? is it worth the money spent on another brand new motherboard? I have a regular asus P7P55D x16/x4 motherboard, say if I upgrade to a msi 890gxm-g65 which has x8/x8, would it be worth the money considering I only have the 5770 which is a mid-range card?

 

[Maziar]

too Helltech
Well you are right about 8x, but as for 16x4x,the loss is more than 10-15%,sometimes it even gets a performance hit of 50% (depending on the game and settings)
to vertical
Definitely its worth it if you look at the link i posted,it says that
"The easy solution for P965 and P35 Express systems is to simply use a single, more powerful card. At the very least, the issue we encountered where a secondary PCI Express x4 slot’s limited bandwidth hurt performance can be avoided by using a single card, so comments such as "CrossFire doesn’t work right" wouldn’t apply to single-card CrossFire solutions such as the HD 4870 X2. But the point of this article was to judge the viability of adding a second card when a reasonably good card is already installed, and this is an area where P965 and P35 Express motherboards simply cannot be upgraded to compete with modern builds."(In which P35 supports CrossFire at 16x4x which is pretty much like your board and P45 chipsets support CrosFire at dual 8x(same as P55).
but you are switching from Intel to AMD which you have to change your CPU too, so IMO buy a P55 motherboard(with dual 8x CF support) and you can save some bucks.

 

[Helltech]

too Helltech
Well you are right about 8x, but as for 16x4x,the loss is more than 10-15%,sometimes it even gets a performance hit of 50% (depending on the game and settings)

Now is that Crossfire only? Could explain why what I found had such contradicting ideas.

 

[vertical777]

oh, right. what would be a good intel mother board that has dual x8 PCIe, ATX form or EATX*, not too expensive and well worth the money?
*EDIT: I remembered, my case was full tower lol

to think that ASUS branded this mobo as "crossfire ready", well maybe the P7P55D-PRO version is, but not this one

 

[Maziar]

Now is that Crossfire only? Could explain why what I found had such contradicting ideas.

Yes that's for CrossFire,but its the same results for single mode too, however i haven't seen any motherboards which have only one PCI-E 4x slot, most of them have PCI-E 16x or 1 16x and one 4x slot, so mostly the comparison is between 16x4x and dual 8x/16x

 

[vertical777]

Best answer selected by vertical777.