How to make a judgement which CPU is "enough" for a video card?

[ibex333]

How do people tell which CPU is fast enough and which is a bottleneck?

Also, what would give better graphics performance? A horribly slow CPU with an extremely powerful/fast video card, or an extremely fast CPU with an anemic video card?

What if the margins were not as dramatic? What if you had a core2duo paired with a 5870 and an i3 2100 paired with 5850? Which would have better gaming performance?


Can you please explain how do you know these things? How do you tell which cpu is a good pair for which video card?

 

[blastingcap]

Is this a real question because your rig is pretty expensive for you to only start asking that question now. I would never skimp on CPU because it is WAY harder to upgrade CPUs than video cards. You MIGHT be able to keep the same motherboard and RAM, but even then it's way more time-intensive to swap CPUs than GPUs which are practically plug-n-play. That said, how much CPU you need may change very soon if Mantle has its way. They did a demo where they artificially decreased the speed of a AMD CPU to half and it still ran fine.

If you don't want to wait that long, just find a CPU-bottlenecking game to give you an idea of what goes with what. For instance:

http://www.techspot.com/review/305-starcraft2-performance/page13.html

That's a worst-case scenario because SC2 is notoriously CPU-bottlenecked as it only uses 2 cores.

 

[nwo]

It depends on the video game settings and environment. For instance, if you are playing multiplayer with a lot of action around you, you will need a fast CPU. For instance BF4 64 player maps. If you don't have a good CPU (OCed) your frame rate will struggle regardless of which video card you have. However, in single player, you can expect smooth fps.

You have to draw the line somewhere though. For example, you cannot game on a 2GHz dual core celeron, it's simply not going to cut it for any modern gaming.

Your question regarding a core 2 duo with a 5870 and an i3 2100 with a 5850 is not really a good example because those two CPUs are both dual cores and they are only one generation apart. Just like the two CPUs you mentioned, those two graphics cards are very close to performance. Therefore, it is safe to say that both systems would perform roughly equal since the core 2 duo is a slightly slower CPU but has a slightly faster graphics card.

 

[el etro]

Use FireStrike/CinebenchR10 for comparsion, but i advice you is not accurate.

 

[bystander36]

The reality is that all CPU bottleneck higher end cards in some games. Whether its a big deal is another story.

My thought is to not skimp on the CPU, as long as you can get a decent GPU as well. I don't mean you need to spend money on those $400+ CPU's, but if you plan to spend that much on a GPU, at least spend that much on the combined cost of MB and CPU. You'll likely hold onto the CPU for at least 2 generations of GPU's. CPU progress is much slower than GPU progress.

I'd most definitely choose the i3 over the core2duo. While both are dual core, the i3 at least has hyper threading, which allows for 4 threads. The small loss on the GPU is smaller than the difference in CPU's.

Edit: The reality is, your CPU choice is often made by your FPS target at any graphical setting. The CPU generally determines the FPS the game will run at when the GPU isn't a factor. The GPU determines the settings you can use based on the resolution you use. I guess if you are ok with 30 FPS, then you can cut corners on the CPU.

 

[escrow4]

Common sense. A $300 280X or $400 290 would be an ideal match for say a $310 i7, an i5 would also be sufficient, but I'd still take that bit of extra grunt from an i7. You wouldn't match a $300+ GPU to a $110 FX 6300 say. From your examples, its time for a new PC. Dual cores are a poor choice for upcoming next gen ports and the 58xx cards have been replaced twice over already, 3 if you count the R9 series.

 

[ibex333]

Is this a real question because your rig is pretty expensive for you to only start asking that question now.

Off course its a real question. I been building computers for years, but the way I do it is I just base my decisions on other peoples builds or I approximate, or I take a chance and hope my build is good. With video cards I usually go as far as my budget can afford.
But I made this post because I am curious how people know FOR SURE. For example, I'd never stick a Radeon 7850 in an LGA 775 system, because these are different generations of hardware. But I am ASSUMING here. What if that video card would work just fine in that system? How do I know? I don't have the money and space to actually try something like this.

You understand what I mean?


But if I understand you correctly, it's not the cpu that limits how far the video card can go, it's just that if a cpu is too slow for a given game it doesn't matter how fast the video card is, the game simply wont run well. Am I understanding you correctly?

Are there any scenarios where the cpu is fast enough to run the game on max settings, but it is not fast enough for the video card to perform at its best? If there are such cases how can one know for sure that this problem exists in their system?

Common sense. A $300 280X or $400 290 would be an ideal match for say a $310 i7, an i5 would also be sufficient, but I'd still take that bit of extra grunt from an i7. You wouldn't match a $300+ GPU to a $110 FX 6300 say. From your examples, its time for a new PC. Dual cores are a poor choice for upcoming next gen ports and the 58xx cards have been replaced twice over already, 3 if you count the R9 series.

My question is purely theoretical. I am not looking to upgrade or play anything specific right now. I am just curious about the concepts and the intricacies of this stuff.

 

[Techhog]

Is this a real question because your rig is pretty expensive for you to only start asking that question now. I would never skimp on CPU because it is WAY harder to upgrade CPUs than video cards. You MIGHT be able to keep the same motherboard and RAM, but even then it's way more time-intensive to swap CPUs than GPUs which are practically plug-n-play. That said, how much CPU you need may change very soon if Mantle has its way. They did a demo where they artificially decreased the speed of a AMD CPU to half and it still ran fine.

If you don't want to wait that long, just find a CPU-bottlenecking game to give you an idea of what goes with what. For instance:

http://www.techspot.com/review/305-starcraft2-performance/page13.html

That's a worst-case scenario because SC2 is notoriously CPU-bottlenecked as it only uses 2 cores.

Is it really? Unless you're upgrading the motherboard too it seems pretty straight forward, and you don't even need to reinstall your OS.

 

[bystander36]

But if I understand you correctly, it's not the cpu that limits how far the video card can go, it's just that if a cpu is too slow for a given game it doesn't matter how fast the video card is, the game simply wont run well. Am I understanding you correctly?

Are there any scenarios where the cpu is fast enough to run the game on max settings, but it is not fast enough for the video card to perform at its best? If there are such cases how can one know for sure that this problem exists in their system?

For most games (not all), no matter what graphical settings are used, the FPS max and minimum potential is the same based on the CPU. A CPU determines the max speed a game is capable of hitting in most cases. If your GPU cannot hit those FPS, you are not bottlenecked.

Anytime your not bottlenecked, your question is true. Most times you are not bottlenecked, the GPU is holding back performance. In some games, both can be holding back performance together, but doesn't seem common. One or the other is holding back performance.

 

[blastingcap]

But if I understand you correctly, it's not the cpu that limits how far the video card can go, it's just that if a cpu is too slow for a given game it doesn't matter how fast the video card is, the game simply wont run well. Am I understanding you correctly?

Are there any scenarios where the cpu is fast enough to run the game on max settings, but it is not fast enough for the video card to perform at its best? If there are such cases how can one know for sure that this problem exists in their system?

Yes and no. Depending on the scenario, either the CPU or GPU is the bottleneck. For some games they are so CPU-intensive that the CPU is almost always going to be the bottleneck as long as you have even a midrange video card (hello, Starcraft 2). But it also depends on graphics settings and resolution as well. For instance, I'm pretty sure that attempting to run Starcraft 2 on a 4K screen at max settings using a HD7750 is going to be a GPU-bottleneck, not a CPU-bottleneck.

One thing you can do is to run MSI Afterburner or similar program that shows GPU load percentage. Then open a game up, turn off Vsync, and play around. Then alt+tab out and see what percentage of GPU load you are at. It should be like 99%. If it's lower, then your CPU was limiting your GPU. That was what happened to me in Fallout 3 when I was playing on a 1055T + 7970. My 3570K + 7970 allows me to hit 99% GPU load in Fallout 3 now.

Is it really? Unless you're upgrading the motherboard too it seems pretty straight forward, and you don't even need to reinstall your OS.

The problem I see is that most of the time in order to get a significant CPU boost you do have to swap motherboards, unless you were doing something crazy like using a cheap i3 Sandy and upgrading to an expensive i7 Ivy. So that means mobo swap and possibly also RAM swap (less likely these days since DDR3 has been around for a while now).

Even if you do not need to swap mobo and RAM, you do still need to remove CPU cooler, swap CPUs, take off and reapply thermal paste, put on CPU cooler. Whereas swapping video cards takes like 1 minute.

Also, the resale market for CPUs is also weak in my experience, compared to used GPUs.

And as someone else pointed out, CPUs improve slower than GPUs so you might as well focus on CPU first and then GPU, and then if you need to you can easily upgrade the GPU later.

Reasonable minds can differ. I just try to buy the highest-performing CPU that isn't outrageously priced and go from there.

 

[nwo]

But I made this post because I am curious how people know FOR SURE. For example, I'd never stick a Radeon 7850 in an LGA 775 system, because these are different generations of hardware. But I am ASSUMING here. What if that video card would work just fine in that system? How do I know? I don't have the money and space to actually try something like this.

You understand what I mean?

I know what you mean.

Here is how I can relate with my side of the story from recent experience.

I don't have any issues running a 4870 in my socket 939 motherboard... Just because the motherboard socket generation does not match the graphics card generation does not mean that they are not compatible with each other. Now, I could have some issues if I wanted to run two or three graphics cards in the same system, because I might saturate the PCI-e lane bandwidth (maybe not with these cards, but perhaps some higher end ones, but that's slightly different topic for discussion.

Just like I did not have any issues installing and running a 100GB SSD OCZ Vertex 2 which uses SATA 2 (3Gbs interface) even though my motherboard uses the first generation SATA 150 (1.5Gbs interface). SSDs were not even in mass production when this motherboard was around!

SATA and PCI-e are both backwards compatible. Which means that if you use a newer standard of what your motherboard supports, its performance may not be optimal because of the bandwidth restrictions. However, the hardware itself will work perfectly fine even though it may not perform to 100% of its capability.

I hope that makes sense.

The only thing you should be concerned about when it comes to motherboards is the CPU (socket type) and RAM (standard such as DDR, DDR2, DDR3, etc) compatibility, everything else is fairly flexible.

 

[KingFatty]

Can't you just pick a threshold FPS number, and then do a check on various games/settings to see if either the GPU or CPU can achieve it?

I mean, I don't give a crap whether one is better than the other, if they both can manage 60 FPS easily. Do I care if the CPU could theoretically reach 999 FPS but the video card could only reach 61 FPS? Nope, together they provide at least 60 FPS so I'm happy.

 

[ibex333]

Fascinating... I find this stuff extremely interesting. Something about pushing old hardware to the limit as opposed to cruising comfortably on new hardware really captivates me. Sometimes I am almost tempted to sell my "modern" rig and use an old one living like a masochist, but certain things I need to do require faster hardware.

I am very comfortable on my main rig (in sig), but I also have a LGA 775 system with e6300 @ 3.20GHz and a gigabyte DS3 mobo. I have another LGA 775 mobo if this one dies and another e6300 to kill as a spare. ; ) Currently there's an ATI Radeon 5450 in there, but maybe I'll score a better video card on CyberMonday to bench this computer with.

 

[Jacky60]

Anandtech needs a test like most websites for checking whether posters are human or not. GPUs are really easy to upgrade, CPU's far less so. You need a top CPU if going with one or more top of the range GPU's BUT a mid range CPU with top end GPU is better than a top CPU with mid range GPU. Got it?

 

[blastingcap]

a mid range CPU with top end GPU is better than a top CPU with mid range GPU. Got it?

Not if you're playing at 800x600 at minimum settings. :colbert:
(That was a joke but there is a grain of truth to it... it really depends on what settings and what game and what resolution.)

 

[ibex333]

Anandtech needs a test like most websites for checking whether posters are human or not.

No it doesn't. God forbid! It's very annoying to type barely discernible capcha every time you want to make a post.

 

[Cerb]

How do people tell which CPU is fast enough and which is a bottleneck?

Typically, by tests run on systems with lots of CPU power to check GPUs, and GPU power to check CPUs, and/or monitoring performance counters on your PC as you game (Task Manager and Afterburner give valuable information, FI).

Also, what would give better graphics performance? A horribly slow CPU with an extremely powerful/fast video card, or an extremely fast CPU with an anemic video card?

N/A. Graphics performance includes both. The CPU does basically everything but the rendering itself, and the rendering is done 100%, or near it, by the GPU. The CPU can work without a GPU, but the other way around is not [yet] possible.

A pure GPU bottleneck would result in the same performance across many CPUs, which can sometimes be seen in GPU reviews, on sites that test several CPU platforms, and high settings and resolutions. A pure CPU bottleneck results in performance scaling approximately the same as the CPU speed gains between similar CPUs. Reality usually finds games to be somewhere in the middle, since high settings tax the CPU more in preparing each frame, especially with SLI/Crossfire, so it's hard to make a pure CPU bottleneck test a reality, though a very slow GPU (relative to whatever test you are using) can allow you to set that up with relative ease.

If the game is pushing too much crap for the GPU to handle, you'll see the following:
1. Lower CPU utilization relative to lower graphics settings.
2. Very low or no performance variation across CPUs, or speeds of an overclockable CPU.

If the other way around, GPU utilization will be low, but CPU utilization high.

Since companies like to make more money from higher-performance products, it usually comes down to budget effects, and that GPUs are easier upgrades than CPUs. Those factors make it easier to pick something.

 

[UaVaj]

this is one of the most asked question of all time. how to properly balance a system.



with kingfatty on this one. choose the game. choose the resolution. choose the in-game setting. choose the minimum fps.

sc2 is great for cpu limited. bf3 is great for gpu limited. bf4 is great for both.
there are enough online reviews to derived satisfactory data for choosing the proper hardware. hardware that is capable of delivering that chosen level of performance.



if anyone knows a different method - do tell.

 

[Jacky60]

Not if you're playing at 800x600 at minimum settings. :colbert:
(That was a joke but there is a grain of truth to it... it really depends on what settings and what game and what resolution.)

It's a basic rule of thumb that generally applies pedantry aside.:\ If you're playing at 800x600 minimum settings then frankly the question is irrelevant it'll still look crap and won't be worth commenting on.
Clearly it 'depends' BUT most modern 4 core CPU's at (with the exception of a few of the more turgid AMD ones) are decent enough to pair with a 280x/770/290/290x/780 whereas I wouldn't want a 4930/4770 with a 7850/660 in Arma 3, BF3/BF4, or Crysis 3 even at 1080.
The point of a generalisation is that it's mostly correct most of the time and a little interweb research for outliers is clearly beneficial if playing anything a little less mainstream.

 

[FalseChristian]

Look, my i5 2500K at 4.5GHz is 3 generations old but is still more than powerful enough to power a GTX 780 Ti SLI or R9 290X XFire sytem. In fact, my cpu will be fine for nVidia's upcoming 20nm GPU, Maxwell.

You would be better off with a good CPU paired with a great GPU.

 

[moonbogg]

People don't know FOR SURE all the time for every game, and who cares anyway because is it really that important? Get the best you are willing to pay for. That's what I do then call it done.

 

[Nebor]

Look, my i5 2500K at 4.5GHz is 3 generations old but is still more than powerful enough to power a GTX 780 Ti SLI or R9 290X XFire sytem. In fact, my cpu will be fine for nVidia's upcoming 20nm GPU, Maxwell.

You would be better off with a good CPU paired with a great GPU.

This. I have an i7 of the same generation (I think?) and I don't anticipate having to replace it in the next several years. I did just swap my gtx580 for a gtx 780 though.

 

[blastingcap]

The people saying oh my CPU is 3 generations old are a) mistaken (Sandy is 2 gens old not 3), and b) this is only because CPUs have hit a wall whereas GPU perf keeps growing because graphics tasks are inherently easier to make parallel than CPU tasks. Prior to Sandy, CPU performance was more important than it is now when you gain a paltry 5% by going from one gen to the next, because Intel is prioritizing perf/watt over raw perf. And even if Intel prioritized raw perf, there are very few games that take advantage of more than a few cores. Almost all old games can't really take advantage of more than 2 cores. Even today, few games can max out 4 cores. Turbo helps only a little in this regard.

In contrast, screen sizes and gfx effects keep marching forward (3D/120Hz/4K/Eyefnity; PhysX, TressFX, etc.), so GPU power is more often the limiting factor than it used to be.

That said, I would never skimp on the CPU, it's too much of a hassle to upgrade relative to a GPU. If someone were building a new system from scratch, I wouldn't advise them to get just enough to get by (which is what, a i3-3220 these days for most games). But if they already had a 2500K or something, then stay on that nasty 2500K, it was, is and will still be nasty-fast for years to come because CPU progress is so slow now and it'll be a while before games routinely max out a stock 2500K let alone an oc'd one. Hell there are people with overclocked i7 920s who are doing just fine.

Exception: if you are running three or more high-end cards, it is recommended to get a high-end CPU or you will bottleneck them. At least a 2500K.

Also, if you like to multitask and have a bazillion programs running at the same time in the background while gaming, then more cores is a good thing, so is a faster-per-core CPU.. I'd get at LEAST a 2500K in that situation, too.

P.S. http://www.tomshardware.com/reviews/fx-8350-core-i7-3770k-gaming-bottleneck,3407-5.html

 

[eno]

ibex, hey I just decided to add some pep to my old 775 system. I replaced the e6300 w/ a free E8400 (thanks Brother in Law) on my Non OC Intel MB. Took out a 6570 1gb DDR3 and dropped in a 7850 MSI TF3 ($93 AR) and I'm sure it's bottlenecked but my in game performance on the one game installed is perfect now. 60fps at full settings on my 1080p LG TV. I know this isn't great info but just saying a relatively cheap new card will still perform well depending on how much your are expecting from it and what game. Down the road I will grab a good deal on i3/mb/ram from newegg and move this old hardware to a different purpose. THe 7850 will open up even more at that point. FWIW.

 

[myfriend]

i guess it really depends on the game but maybe this will help you make a decision

http://www.techspot.com/review/734-battlefield-4-benchmarks/page6.html
i know some mentioned FX63xx for 110 vs 300 i7