CPU bottlenecks with graphics cards

[toscar12]

Hi I'm looking for some information about CPU bottlenecks at lower resolutions and how it works. I'm not to sure if it was better to put this thread in CPU or Graphics and display section but I guess we will see how it goes. Firstly I upgraded to 780 ti sli recently and have discovered something interesting. while gaming on a full hd 1920x1080 TV.
With crisis 3 and sli enabled with max settings and AA on, the game level I was testing I was getting an average fps of 39 and it didn't matter what AA settings I set it at , either the fxaa or 8xmsaa there was barely any difference what so ever maybe 2-3 fps so I found that rather strange.
So I decided to overclock my CPU a bit not knowing what difference there would be.
The difference was incredible I overclocked to 4.5ghz and my average frames went from 39 to at least 60 probably more because I was playing with vsync enabled.
So what I would like to know is this a CPU bottleneck? And what effect does a CPU bottleneck have (or will there even be one) at higher resolutions like 2056x1600 and 4k?
Also what happens when I upgrade to gtx 880 ti sli if I stay at 1080p will my fps even increase or will I just circle the same fps Im getting now?
Thanks for your help>

 

[IDontUnderstand]

What is your CPU?

 

[toscar12]

i7 3930k

 

[toscar12]

I feel stuck like there is no point upgrading it because there is nothing really faster than it unless I overclock and getting a CPU that overclocks well feels like a super expensive lucky dip

 

[IDontUnderstand]

In this review, they were running an i7 SBE and got a pretty good performance in Crisis 3
http://www.guru3d.com/articles_pages/gtx_780_ti_sli_geforce_review,8.html

I really doubt it's the CPU is causing the bottleneck.
So max settings with GTX 780 Ti was only giving you 39?
and with the exact settings and an overclocked CPU, it gave you more than 60?

Update: In these two threads, it tells me that Crisis 3 is very CPU intensive and also clock speed sensitive.
http://www.overclock.net/t/1362591/gamegpu-crysis-3-final-gpu-cpu-scaling
http://www.techspot.com/review/642-crysis-3-performance/page6.html
Good benchmarks to read through.

 

[Supernova1138]

Crysis 3 is infamous for being extremely CPU heavy, and is one of the few games where you would hit a bottleneck with that CPU at stock clocks when running 2 780Tis in SLI. Most games won't be quite that CPU bound, and will give your graphics array more of a chance to shine. I will say that 1080p is a rather low resolution for your GPUs. Generally you don't really benefit from that much GPU horsepower unless you are running at least 2560 x 1600 resolution.

You are much less likely to see a CPU bottleneck at a higher resolution as your graphics cards will have more work to do. As you said, there's not much reason for you to upgrade right now, there are few CPUs that are better than what you have, and they aren't that much better. If you do want to upgrade something, I would say either get a higher resolution monitor, or go for a triple monitor surround setup if that's your thing. I wouldn't bother moving up to the next generation of GPUs when they do come out until you move up to a higher resolution, because frankly your current setup is already overkill for 1080p.

 

[IDontUnderstand]

Crysis 3 is infamous for being extremely CPU heavy, and is one of the few games where you would hit a bottleneck with that CPU at stock clocks when running 2 780Tis in SLI. Most games won't be quite that CPU bound, and will give your graphics array more of a chance to shine. I will say that 1080p is a rather low resolution for your GPUs. Generally you don't really benefit from that much GPU horsepower unless you are running at least 2560 x 1600 resolution.

You are much less likely to see a CPU bottleneck at a higher resolution as your graphics cards will have more work to do. As you said, there's not much reason for you to upgrade right now, there are few CPUs that are better than what you have, and they aren't that much better. If you do want to upgrade something, I would say either get a higher resolution monitor, or go for a triple monitor surround setup if that's your thing. I wouldn't bother moving up to the next generation of GPUs when they do come out until you move up to a higher resolution, because frankly your current setup is already overkill for 1080p.

I totally agree with you, but I don't understand how an overclock can bring his FPS up by so much, or was he testing it wrong?

 

[Supernova1138]

I think it's just a unique situation with Crysis 3, that game is just ridiculously CPU heavy compared to just about any other title. The OP also overclocked his CPU 1300MHz above stock speed, which would provide a pretty significant CPU performance bump, quite possibly enough to cause that big of a jump in performance.

 

[toscar12]

nope it really does bring the frames up that much I think it is bottlenecking or maybe just the overclock gives such a large increase and I have double checked it numerous times. thanks for the info and threads by the way I will give them a read

Supernova1138> Im actually getting a 4k TV soon so could you explain how there will be less of a bottleneck I'm still not sure how that works?

 

[toscar12]

Supernova1138> so you don't think there is a bottleneck?

 

[Supernova1138]

When you move to a higher resolution, your GPU has more work to do because it needs to render more pixels, this shifts the balance of your workload more towards your graphics cards, and if you are moving all the way up to 4k, then you definitely won't have a CPU bottleneck as your GPUs will be working at 100% just to deliver playable framerates at that resolution.

The reason you hit a CPU bottleneck at 1080p aside from Crysis 3 needing a ton of CPU power was you had way more GPU horsepower than you needed for that resolution, so much so that your GPUs were waiting for the CPU to feed them data rather than churning out frames, as such some of your GPU horsepower was going to waste. Overclocking your CPU seems to have alleviated that problem for Crysis 3, and you likely aren't hitting much of a CPU bottleneck anymore for that game. Maintain that overclock so that your graphics cards remain fed with data and they both should be running at 100% when you get a 4k display, especially running Crysis 3, I don't think even 2 780Tis can max out Crysis 3 at 4k resolution.

 

[toscar12]

LoL No I don't think they will! ,probably 40 fps on very high with no AA if I am lucky, according to reviews I have read. I am looking forward to playing my old favourites on 4k though. Anyway thanks for the information that was exactly what I was looking for!