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HD 5850 3-way crossfireX vs HD 5850 2-way crossfireX

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June 11, 2010 6:39:31 PM

Hi all, I hope this is not going over old ground but I am building a new system and was wondering what the performance gain (if any) there would be in running a HD 5850 in 2-Way Crossfire against a HD 5850 3-Way Crossfire configuration? I will be using a 1920 x 1080 monitor with a 1000watt PSU and an overclocked i7 930 @ 4GHz and 6Gb of DDR3 Ram, which I hope will be good enough for either setup.
If the consensus is that 3-Way Crossfire is just not worth it then I will go for 2-Way.
Thanks in advance.
June 11, 2010 6:48:09 PM

The benefits gained from crossfiring are significantly less with each subsequent card, meaning that upgrading to 3-way is not going to be a full 50% increase in performance. Why not get a 5970 anyway? What games are you going to play?
BTW, a i7 @ stock probably wouldn't bottleneck, so you'll be fine.
June 11, 2010 6:54:03 PM

Hi, I already have a HD 5850 in my current system so it just made sense to keep it and add either a second or third card to the setup. I am doing a one off purchase so what I get now is what I shall have for the next couple of years.

I will be playing COD MW2, 2033, Wolfenstein, Bioshock 2, etc etc I think you get the picture.

Thanks
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June 11, 2010 7:26:43 PM

I have 2 5850s and they can play anything at highest detail. Solid framerates in Crysis and Metro 2033. You gain about 50-85% in crossfire. I don't know how well a 3rd card would benefit... like jryan says tho it's not as much. Especially if the 3rd PCIe is only able to run at 4x it'll really gimp it... 8x is just fine tho.

You can see some benchmarks I ran showing how CF improves over a single card, but again I don't know how well a 3rd card will help
http://www.tomshardware.com/forum/289809-33-single-5850...
June 11, 2010 7:32:40 PM

Just looked and it has 4 x16 slots
June 11, 2010 7:35:47 PM

Thanks. I forgot to mention that the MoBo is an ASUS Rampage III Extreme which I believe is either x16, x16, x16 or x16 x16 x8 on the graphics lanes.
June 11, 2010 8:53:42 PM

gonesy is correct, the Rampage III Extreme can do x16/x16/x16 or x8/x8/x8/x8. Technically there are 4 x16 slots but once all 4 are ocupied it defualts to x8/x8/x8/x8.

Here are the complete PCI-E specs :

Expansion Slots:
- 4 x PCIe 2.0 x16 , support x16; x16/x16; x16/x8/x8 and x8/x8/x8/x8 configurations
- 1 x PCIe x4
- 1 x PCI 2.2
June 11, 2010 9:01:27 PM

Well it can definitely run trifire pretty well but the question remains whether or not 3 cards will scale well enough to warrant doing it. IMO if you're considering $900 for graphics cards, sell the 5850 on ebay and get crossfire 5870s or a single 5970 (the CF 5870s will be faster). Tho 2 5850s is still ridiculously fast and for the time being no game can bring them to their knees.
June 11, 2010 9:25:02 PM

Dual 5850's overclocked/overvolted should be plenty, i dont see the 3rd 5850 pushing out that much oomph compared to the first 2. Also take into consideration that out of all 4 games that the OP posted the only one that will bog down the cards is 2033 at max settings.
June 12, 2010 9:31:02 AM

Thanks for the input. I think that the consensus is that 2 x 5850's will be more than enough for now. I keep reading about tessilation coming to games in the near future and was wondering if the dual setup will give good tessilation in future games? Like I said before this is going to be a one time build so I want to get it right.

Many thanks
June 12, 2010 9:44:56 AM

gonesy said:
Thanks for the input. I think that the consensus is that 2 x 5850's will be more than enough for now. I keep reading about tessilation coming to games in the near future and was wondering if the dual setup will give good tessilation in future games? Like I said before this is going to be a one time build so I want to get it right.

Many thanks

Something else for you to consider even though you may have already decided what you intend to do.
Quote:
Now before we start with the conclusion and everybody starts yelling oooy Hilbert, where are the 3-way CrossfireX results, here's the thing: I have three R5870 and three R5850 cards arranged especially for this article series to compare to. Now, we always say it ... the more GPUs you add, the more problems you can run into. Make no mistake, that rule applies to both ATI and NVIDIA. Unfortunately things for ATI became problematic. Our test system worked perfectly fine in 2-way ATI CrossfireX mode, but adding a third card would just not frickin work. It's an odd bug that we have encountered numerous times in the past already. Though the driver installation works fine and the (in this case 5850) products are recognized fine somehow ATI Catalyst decides to disable the 3rd adapter. Intriguing, puzzling, irritating yes .. but non-solvable with the limited time at hand for this article.


Source.

It's all about diminishing returns, as others have already said.
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