Relation Between CPU and GPU

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NExUS1g

Gawd
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Aug 15, 2004
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I hope I'm putting this in the right location. (I'm asking here because I'm looking at buying video cards soon.)

At any rate, I wanted to know what exactly the relation is between the CPU and the GPU. I know this is probably a lot more complex of an issue than a simple question. Let's say that I have a Crossfire setup with two 5970's and an i7 920 at 4 GHz, will the processor strangle the video cards' ability or will the video cards still be the bottleneck on the system? Is there some way to figure this out? I tried searching for like a "calculator" or chart that I could use to determine the CPU need in relation to the GPU, but I couldn't find anything like that.

Thanks.
 
Ignoring all the technical issues, it really depends on the game. Some are more CPU intensive and some are more GPU intensive.
 
I guess that's the rub then, because I play lots of different games from Batman: Arkham Asylum to StarCraft Brood War, from Call of Duty: MW2 to Counter-strike 1.6.

/edit: Though I think what more of the question is, will the GPUs be able to max themselves out (given the above scenario) or will the CPU prevent that from happening?
 
It also depends on the resolution. CPU load doesn't increase nearly as much as GPU load does as you crank up the resolution. Likewise, things like AA and AF have zero impact on CPU usage.

But really, you've got the best possible setup so it doesn't even matter if its your CPU or GPU holding you back as you've got nowhere to go.
 
with 2 5970s (4 GPUs), driver support is not good enough to keep all the GPUs fed, which results in significant diminishing returns and in some cases, a decrease in performance.
 
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Short answer: If you have an i7 running at 4GHz or higher, the only times you will be CPU bound is for certain games that are CPU bound no matter what CPU you have. Some of these include GTA IV, Supreme Commander and Flight Simluator X. There's really nothing you can do to avoid being CPU bound in games like that.
 
Looking at some of those articles listed by others in this thread, I am feeling really bad about having a q9550 right now.
 
leh18621 said:
Looking at some of those articles listed by others in this thread, I am feeling really bad about having a q9550 right now.
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That 260 is what is going to be holding you back 95% of the time, so don't feel bad about the cpu.
 
NExUS1g said:
That's a really good site. Almost exactly the kind of thing I was looking for. What search string did you use to find that or did you just have a link to that just lying about?

Thanks to everyone for the good info.
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I have a large number of hardware sites bookmarked. Legion is simply one. I tend to check most of them fairly regularly.

If you're interested in the sites I check, try below.

http://www.hardocp.com/
http://techreport.com/
http://www.extremetech.com/
http://www.legitreviews.com/
http://www.beyond3d.com/
http://www.bit-tech.net/
http://hothardware.com/
http://www.rage3d.com/
http://www.hardwareheaven.com/
http://www.techpowerup.com/
http://www.nvnews.net/
http://www.hardwarecanucks.com/
http://www.guru3d.com/
http://www.firingsquad.com/
http://www.anandtech.com/
http://www.pcper.com/
http://www.bjorn3d.com/
http://www.legionhardware.com/
http://www.madshrimps.be/
http://www.sharkyextreme.com/
http://www.xbitlabs.com/

For Overclocking

http://www.xtremesystems.org/forums/index.php

When new video cards or CPUs come out I'll usually try to check them all for reviews. I regard [H]ard's results the highest usually because they take the time to play through demanding areas in games rather than looping time demos or canned benches. I find it's easier to get a accurate picture when I read as many reviews as I can. If you want to read some seriously technical opinions on GPUs try haunting the Beyond3d forums.
 
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evilsofa said:
Short answer: If you have an i7 running at 4GHz or higher, the only times you will be CPU bound is for certain games that are CPU bound no matter what CPU you have. Some of these include GTA IV, Supreme Commander and Flight Simluator X. There's really nothing you can do to avoid being CPU bound in games like that.
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I will 2nd that,

I noticed that you are talking about 4ghz our higher, are we talking overclocking? Generally i try not to over clock and run two graphics cards. It might be less of an issue now however, haven't overclocked in awhile. At some smaller end cpu you can run into problems loading high quality vidoes and stuff, however at your speedits a none issue. True is it all depends on the game, supreme commanders biggest limitation is CPU due to the calculation the game does. Truth of the matter is i wouldn't worry about it
 
People won't "feel" FPS differences when you're talking about getting 65 vs 78FPS. Now if overclocking raises your min FPS from 21 to 29, you'll likely notice that. Slow downs won't be felt as much. I've tried running my rig at my max CPU clock and @ 3.2. I definitely lose both min and avg FPS without touching my card clocks. I see no reason to leave performance on the table when I need not do it even if we're only talking about 8-15FPS. When that's impacting averages in the 70FPS range I couldn't care less. When it's getting subtracted off my min FPS I care if I'm dealing with possible mins in the 30-40 range. I prefer to have a 30FPS min or better at all times.
 
Fantasysage said:
That 260 is what is going to be holding you back 95% of the time, so don't feel bad about the cpu.
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I am planning on getting one of the expected refresh cards around the end of the year (5890? GTX 485?). I figure it will be my last gpu upgrade in my current system. I just hope my q9550 can hold up another two years with a gpu upgrade.
 
Basically put, to render frames in most games you need some CPU time and some GPU time, the CPU does things like re-calculate the state of the world, where the players are, the items, who is shooting, who is moving, it processes all the netcode to/from a server and a whole bunch of other things.

Once the game world has been updated the frame needs to be drawn with all the new positions of all the objects/models/players/projectiles etc, this is done by the GPU.

Now each game is different and requires a different amount of CPU and GPU time depending on what sort of game it is, a fairly standard FPS game for example tends to use lots of nice graphics and requires a lot of GPU rendering time and not that much CPU time...where as a game like The Sims 3 uses a lot of CPU time to work the AI, and doesn't require much GPU time because the graphics are really simple.

The best thing to do is get a roughly balanced system, if you aim for a high end GPU its worth getting a high end CPU, for a 5970 you should be looking at a reasonably high end quadcore CPU, in fact to be honest most people playing modern games should be looking at a quadcore CPU.

At the end of the day one component is always going to be a bottleneck in some games, you'll never balance it perfectly so it's not worth worrying about too much, you should only worry about bottlenecks up to your target frame rate, about 60fps for me, once above that it doesn't matter which is the bottleneck anymore.

One thing to keep note of is that games tend to have a lot of graphics options for scaling graphics, but hardly any for CPU usage, so when you become CPU bottlenecked theres only really one solution, get a faster CPU (either buy one, or overclock). However GPUs have a plethora of graphics options even when the game itself doesn't have many to chose from you can vastly scale performance by altering screen resolution, AA and AF. So in some respects the CPU is more important becausae if that becomes the bottleneck there's not much you can do.
 
PrincessFrosty said:
Basically put, to render frames in most games you need some CPU time and some GPU time, the CPU does things like re-calculate the state of the world, where the players are, the items, who is shooting, who is moving, it processes all the netcode to/from a server and a whole bunch of other things.

Once the game world has been updated the frame needs to be drawn with all the new positions of all the objects/models/players/projectiles etc, this is done by the GPU.

Now each game is different and requires a different amount of CPU and GPU time depending on what sort of game it is, a fairly standard FPS game for example tends to use lots of nice graphics and requires a lot of GPU rendering time and not that much CPU time...where as a game like The Sims 3 uses a lot of CPU time to work the AI, and doesn't require much GPU time because the graphics are really simple.

The best thing to do is get a roughly balanced system, if you aim for a high end GPU its worth getting a high end CPU, for a 5970 you should be looking at a reasonably high end quadcore CPU, in fact to be honest most people playing modern games should be looking at a quadcore CPU.

At the end of the day one component is always going to be a bottleneck in some games, you'll never balance it perfectly so it's not worth worrying about too much, you should only worry about bottlenecks up to your target frame rate, about 60fps for me, once above that it doesn't matter which is the bottleneck anymore.

One thing to keep note of is that games tend to have a lot of graphics options for scaling graphics, but hardly any for CPU usage, so when you become CPU bottlenecked theres only really one solution, get a faster CPU (either buy one, or overclock). However GPUs have a plethora of graphics options even when the game itself doesn't have many to chose from you can vastly scale performance by altering screen resolution, AA and AF. So in some respects the CPU is more important becausae if that becomes the bottleneck there's not much you can do.
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Out of curiosity, with gpu upgrades how long are you expecting to continue to use your overclocked q9450? Or maybe I should say, how long do you expect that you will be able to use it for gaming before you absolutely have to upgrade?
 
Well I've had it since my 8800GTX, it served me well through my 2x 4870's and I expect it to last this current generation until ATI bring out a potential 6xxx series, or more likely the Nvidia 5xx series.

It's holding up very well, BFBC2 is probably one of the newer CPU hogging beasts for whatever reason, and the Q9450 chews through that and provides me with a decent 60-100 fps. It would probably be starting to struggle in games like BFBC2 if it was at stock 2.66Ghz I suspect.

I think at these clocks it'll easily power my 5970 for this generation, about another 18 months. Then it will be a whole system upgrade and Garrett6 will retire it's aged components and Garrett7 will be born. With any luck Intel will have a new range of performance CPUs to top the I7 range and I'll do what I usally do and invest in the latest performance range but the slowest chip, and overclock the balls off it :)
 
PrincessFrosty said:
It's holding up very well, BFBC2 is probably one of the newer CPU hogging beasts for whatever reason, and the Q9450 chews through that and provides me with a decent 60-100 fps. It would probably be starting to struggle in games like BFBC2 if it was at stock 2.66Ghz I suspect.
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Thank you for responding. I play BFBC2 also with my cpu at the stock 2.83ghz and I have no problem keeping a minimum 40fps. I am guessing that you are getting better fps because your gpu is a lot better than mine (and not because your cpu is clocked higher).
 
leh18621 said:
Thank you for responding. I play BFBC2 also with my cpu at the stock 2.83ghz and I have no problem keeping a minimum 40fps. I am guessing that you are getting better fps because your gpu is a lot better than mine (and not because your cpu is clocked higher).
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I would OC that puppy and start playing at 60fps+. I can't get how people can play multiplayer games with less than 100fps or less than 120hz.
 
My 3.9Ghz OC'd 9550 is a champ in games. I wouldn't worry too much about it being obsolete in the near future. You may notice many around here recommend it as the best upgrade path for those sticking with 775. (Say, running a q6600 currently.)

Basically it's a great chip that holds it's own.
 
med1kl said:
I can't get how people can play multiplayer games with less than 100fps or less than 120hz.
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Because most people have 60Hz LCDs and can't see anything over 60 FPS? Unless you're on one of the true 120Hz displays it's a placebo effect.
 
Little_4nic8er said:
My 3.9Ghz OC'd 9550 is a champ in games. I wouldn't worry too much about it being obsolete in the near future. You may notice many around here recommend it as the best upgrade path for those sticking with 775. (Say, running a q6600 currently.)

Basically it's a great chip that holds it's own.
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I have played around with overclocking my q9550. Rencently, just for kicks I overclocked it to 3.2 just to see how it ran on my cpu cooler (I have a Mascool 8WA743 cooler). Overclocked to 3.2ghz It idled at around 35c, and after 12 hours of Prime95 maxed out at around 55c. I thought this was pretty good on just an ok aftermarket cooler.

Based on that, I am thinking of going to 3.4ghz. Any higher than that I will start to worry about temps because of my cooler and I don't want to buy another better one, and power consumption.
 
PrincessFrosty said:
It's holding up very well, BFBC2 is probably one of the newer CPU hogging beasts for whatever reason, and the Q9450 chews through that and provides me with a decent 60-100 fps. It would probably be starting to struggle in games like BFBC2 if it was at stock 2.66Ghz I suspect.
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The reason is probably because it's a console port and consoles typically have more CPU power than they do GPU power so the game engine has to be coded accordingly.
 
NExUS1g said:
That's a really good site. Almost exactly the kind of thing I was looking for. What search string did you use to find that or did you just have a link to that just lying about?

Thanks to everyone for the good info.
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that is some interesting info but it also points something out about your question. the data there doesn't meant that much. for one thing its showing the phenom II being pretty close to the i7 (in other things it usually gets crushed), enough so that there would be no difference in game play. and for most games that will be true. you really only need a cpu fast enough to feed the video cards for your games. unless your going for quadfire/sli it isn't needed. everything I do runs just fine on the mid range quad core

the rub against the above is that it does sometimes make a difference. If you go and look the H real world cpu scaling you will see that it does afect game play in a couple of games (I am actually suspicious of this, why a cpu would affect the level of AA I can't figure, I am leaning toward that having been a driver issue). it might also be that the cpu simply more important in running crossfire then in single gpu systems (this was a grip I had with H, why test cpu scaling in quadfire? that introduces a large overhead) regardless a difference does exists.
 
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