What clock CPU to avoid Tri-SLI bottleneck?

[thepregnantgod]

I just purchased my third GTX570 1.2gb RAM for a tri-sli setup on my Asrock Extreme 7 Gen 3 (Z68 mobo). I'm using an i7 2600k @ 4.5ghz 24/7.

I will be gaming on a 2560x1600 30" monitor.

My question is: what cpu speed (overclock) should I push to ensure the cpu doesn't bottleneck the graphics cards?

Thanks.

 

[bystander]

You should be good at 4.0Ghz or higher. Even stock is fine. What cards do you have in tri-sli? 670's or 680's? If so, you will likely see some bottlenecking of the CPU, but mostly only because you are getting more FPS than your monitor can display. Two 670's or 680's should be plenty to power that monitor size with a 60hz refresh rate. Though the 3rd will allow for closer to max settings on the rare game with settings generally unplayable by normal systems, like Metro 2033 with advanced DoF, or The Witcher 2 with Ubersampling (still not likely able to use that).

Edit: doh, I missed the mention of 570's right at the beginning (or forgot). Anyways, your biggest issue is going to be memory. 1.25Gb of vram is likely going to be the main limiter in games like BF3. You may be best off just sticking with 2 if it's not too late, and just upgrading completely later on. As you push higher and higher on the GPU power, more vram becomes needed.

 

[geekapproved]

I just purchased my third GTX570 1.2gb RAM for a tri-sli setup on my Asrock Extreme 7 Gen 3 (Z68 mobo). I'm using an i7 2600k @ 4.5ghz 24/7.

I will be gaming on a 2560x1600 30" monitor.

My question is: what cpu speed (overclock) should I push to ensure the cpu doesn't bottleneck the graphics cards?

Thanks.

Isn't the 3rd slot 4x pci-e 2.0?

 

[geofelt]

Isn't the 3rd slot 4x pci-e 2.0?

A very good point.

With the third card at X4, I think the performance will be worse than with dual cards @x8/X8.
SLI can only operate at the lowest common denominator of card capability.

I think the OP would be better off to sell the GTX570's and buy a single GTX680, or wait for the GTX780.

As to the OP original question, he is not going to do significantly better attempting to OC past the current 4.5.

 

[thepregnantgod]

I believe the third slot is also PCI-E 2.0 x8 (not x4).

http://www.asrock.com/mb/overview.asp?Model=Z68%20Extreme7%20Gen3

Am I reading something wrong?

With only two cards, they are x16/16 - the third drops it down to x8/x8/x8.

 

[geofelt]

You are correct. The N200 chip gives you that capability.

 

[thepregnantgod]

So, geofelt, do you still believe I'll see any performance and/or bottleneck with GTX570x3 @ 2560x1600 with an i7 2600k/4.5ghz? I can push the clock higher but my temps are around 66 under load and that's usually my limit.

 

[geofelt]

My guess is that the third GTX570 will look good in benchmarks, but you will not feel much difference in gaming.
Similarly, I don't think a higher overclock will be felt either.

You might try a test with your games, and reduce the OC from 4.5 and see if you can tell any difference in actual gameplay.
If you see any reduction in fps, then you might assume that the cpu is a limiting factor, and that a faster chip or higher oc will do you some good.

It is hard enough to get two disparate graphics cards to render their parts in sync, let alone three.
I wonder if you might be subject to microstuttering, even if you have three high end cards.
You might want to read this article on microstuttering:
http://www.tomshardware.com/reviews/radeon-geforce-stutter-crossfire,2995.html