Will my Phenom bottleneck 6870 crossfire?

[Martin 71]

Hey,
I just took the plunge and sold my 5850, and grabbed 2 6870's and a new case. Then I ran into another forum asking about cpu bottlenecks. Will my quad bottleneck my 6870s? I'm pretty freaked out. Thanks

 

[ghnader hsmithot]

Yes it would.
With that much graphic processing power you would definitely run into bottlenecks.

 

[Martin 71]

even with a 3.8 ghz oc?

 

[Baralis]

A PII even at 3.8 can bottleneck CF 6870's but the extent of the bottleneck will depend alot on the game and your resolution. Some games are more heavily dependent on CPU and others GPU. Most modern games at higher resolutions tend to lean more towards GPU.

You should still see higher frames in all modern games so it is an improvement over a single card setup. If you are happy with the results that is all that really matters. Personally I look for real performance over numbers. If I'm getting 80fps or 300fps it matters little to me as long as my min frame rate is exceptable. No system is going to be perfectly balanced under all conditions, you will always have something that bottlenecks sometimes.

A PII @ 3.8 and CF 6870's should give darn good performance with any modern game. I don't think any bottleneck that you may encounter will be enough to grossly hamper game quality.

 

[Martin 71]

but doesn't a cpu bottleneck cause stuttering and lag?

 

[sportsfanboy]

The stuttering thing is more of a worst case scenario, your more worried about the full capability of your cards being held back. At 3.8 your chip performs similar to a i5 760,and I'm sure plenty of people are running crossfire on that setup. Are you bottle necked? I think maybe a little, however it shouldn't effect function and ultimately game play. I would overclock a little more if you can,if not I wouldn't worry about it.

 

[BaronMatrix]

There are a lot of factors involved with the CPU. What resolution are you running at? Which games are you playing? ANd probably a few more. What you'll probably find if you look at reviews is that if you're running above 1920 the CPU is almost irrelevant.

I saw one recently that showed even a Propus (quad with no L3) can run games at high res.

The short answer is no. Not at 3.8GHz.

 

[Martin 71]

so, what you're saying is that as long as the gpus are given enough work to do they wont be bottlenecked by the cpu... okay. And if they don't have enough work to do then the cpu will limit fps. But it won't limit it a ton anyway, and the gpus are going to deliver a little less than if they weren't held back, but it will still be a decent fps count.

 

[sportsfanboy]

Yes and no, you can't run a P4 prescott with a good video card or cards and run battlefield 3 at 1920 pixels. It means after a certain resolution, the cpu doesn't work any harder and the gpu does.

 

[Martin 71]

Thanks so much I appreciate all your help and I am much happier about my purchase. Thank you!

 

[ghnader hsmithot]

Thanks so much I appreciate all your help and I am much happier about my purchase. Thank you!

HI!
IF you have been seeing the gaming benchmarks of some cpus then you would know how the bottlenecks be like.
Take for example Phenom II X4 965 BE vs i5 2500k and look at the gaming benchmark.
http://www.anandtech.com/bench/Product/102?vs=288

YOu would seee the obvious difference in gaming performance.The more powerful the gpu the more discernable the difference is.

 

[Raidur]

http://alienbabeltech.com/main/core-i7-vs-phenom-ii-x2-vs-x4-scaling-performance-analysis/12

Crysis with 4xAA, so very GPU intensive, still showing weakness in 5870 crossfire.

A 5870 is a bit stronger than a 6870, but only has 40% crossfire scaling compared to 6870's 90%. So they'd be similar or the 6870 crossfire will lead by a decent amount.

You can see nearly a 25% difference in performance on even a GPU bound game with GPU bound settings from the i7 with them both @ 3.8ghz @1920x1080.