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6950 crossfire bottleneck

Last response: in Graphics & Displays
August 5, 2011 7:46:55 AM


I'm thinking about buying the second 6950 2GB, i'm not sure about the bottleneck issue.

I have phenom xII 550 black edition OC to 3.7 Ghz with 4 cores (2 unlocked)
8 GB 1333Mhz ram, Gigabyte UD4P mobo, 650w psu.

Do you think that there will be bottleneck if i buy second 6950 2GB?

a b U Graphics card
August 5, 2011 8:49:13 AM

All Phenoms exhibit some slight degree of inherent bottlenecking (lower average/peak framerates compared to i5/i7), but, the same degree of improvement (50-80% boost) in framerates should occur with the adding of/successful Crossfiring of a 2nd 6950....
August 5, 2011 9:58:20 AM

Maybe not so much a bottleneck issue - but there will be a power one. You will need to get an upgrade for your psu.
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a b U Graphics card
August 5, 2011 10:03:50 AM

hmm what psu do you have, in terms of bottlenecking, I would say that a better cpu would certainly benefit the xfire 6950.

In terms of power, I have I5 2500K @4.6GHZ 8GB ddr3, 2 x 6950 flashed to 6950 running on a coolermaster gx 750w.

a b U Graphics card
August 5, 2011 10:28:41 AM

What resolution are you using? It makes a big difference to where the bottleneck is.
August 5, 2011 10:42:29 AM

Thanks for replies.

My resolution is 1920x1080.
I can buy a new psu, 750 or 850w etc.

For example at this resolution, if dhicks19's system gives 100fps in crysis 2 , how would the cpu difference effects the fps?
95? less?
a b U Graphics card
August 5, 2011 10:53:15 AM

Make sure its a decent power supply brand such as corsair. Its really hard to tell what the difference in fps will be. But your cpu is getting dated. First buy the gpu then when you have the cash, get a new cpu.
a b U Graphics card
August 5, 2011 10:57:28 AM

This is at lower res. but increasing it puts more work on the GPU than the CPU also you are just over the 3.5GHz so you can get a bit more:

There is no 1080 bench mark or dual 6950 but the dual 6970 at 1680 x 1050 will be close see:

So your CPU can do around 35 min FPS 50 Avg FPS and 2 x 6950s can do around 48 min 69 avg and a single one around half that. In conclusion your CPU will bottleneck a second 6950 to run around half way between a single and dual cards in Crysis 2 at 1920 x 1080 based on approximate data.
BTW I have exactly the same CPU at the same clock and unlock.
August 5, 2011 11:30:19 AM

A new 6950 with new psu will cost me approx 500$ here in turkey. But if i decide to go for a cpu upgrade, "cpu(i5)+mobo+psu+gpu" costs min 1100$

So in this case, it looks like it's not worth xfire. May be i should wait until new cpu series come out, to build a new pc.