Two 5770's in 8x CrossfireX?

[xGaffner]

Well as title really. I really wanted a 5870 because i just upgraded my monitor but there is absolutely 0 in stock and my 4850 just isn't cutting it at 1920x1080. How much performance exactly would i lose with two 5770's in CrossfireX running at 8x bandwidth (i5)?

 

[Ritsugamesh]

I remember seeing a comparison chart of this, and I believe that at high resolutions you lose somewhere between 1-4% fps which in the grand scheme of things is nothing, bear in mind that's percentage so probably lose 1-2fps per game in x8 configuration.

It'll be a nice fast set-up either way for that resolution.

 

[David-Stephens]

Running two 5770 at 8x
Running at 24" as well and my bench scores have shot up from my 4870 512mb

Pleased though a few issues atm with drivers and some lock ups might be my 520w psu but sorting it, part of the fun of new tech

 

[thebandit]

Lose compared to what ?
Anandtech have a good article comparing crossfire on a P55 and X58 mobo.
**********LINK FIXED*************
http://www.anandtech.com/mb/showdoc.aspx?i=3649
bare in mind though this isn't a pure 16+16 vs 8+8 lanes comparison its also triple channel mem vs dual etc, hence my question above, there is no way to compare P55 16+16 vs 8+8.
So comparing sk1156 with 8+8 and sk1366 with 16+16 you "lose" about 2-7%. However in your set up you can only really say you gain what ever crossfire gives you or go and buy a x58 setup and then you will gain about 2-7% more.

reading this back sounds like I'm being a bit of a nob , I don't intend it like that, all I'm saying is you will gain loads by going crossfire and 8+8 lanes crossfire might not be quite as quick as 16+16 but you would have to buy another CPU, mobo and RAM to get 16+16, so really the question is mute.

 

[LoadsaMoney]

Will be fine if they PCI-E 2.0 slots, be like running on the old 2x16.

No article on that link above, just takes you to the search page.

 

[phod]

This review compares a single 5870 running at 1x,4x,8x and 16x.

http://www.techpowerup.com/reviews/AMD/HD_5870_PCI-Express_Scaling/25.html

Even at 4x performance only dropped 5%, at 8x performance dropped 1-2%
Would have been more helpful if they had done the test with 2 cards in crossfire but their conclusion was good for 8x/8x

Our bottom-line on this subject is that there is every reason to be optimistic when opting for two of these accelerators on motherboards with two PCI-Express 2.0 x16 (electrical x8) slots, because the performance penalty between that and PCI-Express 2.0 x16 (electrical x16) is just too small.

 

[feeddagoat]

Is there no way to limit PCI-E lanes on LGA1366 to x8/x8 and test compared to x16/x16 on the same board and processor? Would be a much fairer test.

 

[TUNSTALL_NICK]

anythings better than a single card imho!