How to Determine GPU vs CPU Bottlenecks and Possible Solutions


bottleneck-image

What is a Bottleneck?

A bottleneck, when talking about computer hardware, and not your favorite rustic libation, refers to the slowest device in the system. That one piece of hardware that is bogging down everything else.

Your hard drive is a typical example. It is almost always the slowest turtle in the race. In fact, nothing much happens until it can deliver the bits of information the CPU needs to actually begin doing something. You have probably noticed that some of your big applications take a long time before anything happens– you can most likely blame that on a slow hard drive. Not always, though…

The same situation holds true for every component in your computer. Basically, your computer is only as fast as its slowest component, whether it be your Central Processing Unit (CPU), the Graphical Processing Unit (GPU), Random Access Memory (RAM), and/or the Front Side BUS (FSB). All of them have to work together by passing along and processing information at a speed that isn’t too fast for any other single component. This can be a tricky piece of electronic real estate to traverse.

CPU vs GPU Bottlenecks

Today I just want to focus on the CPU and GPU issue. Many lucky people will be getting a state-of-the-art game for Christmas. Some of the luckier ones will also receive a brand-spanking new graphics card, too. As wonderful as the prospect may sound, it could lead to unforeseen problems.

If your fancy new GPU is too fast for your CPU, then your CPU will hold back your whole gaming experience. If your new GPU is actually delivering information to a faster CPU, then your fancy new GPU would be a waste of money. Once again, you won’t see any performance gains.


How to Determine Which One is the Culprit

I’ve seen this question posed at forums and web sites I visit and it keeps getting asked over and over again. For years now.

The question will go something like this: “How do I determine whether it is my CPU or GPU that is bottlenecking my system?”

They will then list their computer components. <– this is their mistake because then, these are the types of answers they get:

“Your system is fine the way it is.”, or “Your GPU should be upgraded.”, or the ever-present Troll will say, “That computer is crap!”.

None of the above responses answers the original question. The poor guy/gal wanted to know how to figure it out for themselves.


Well, I’m here to show you the simplest, easiest way I know to do just that.

What You’ll Need

The numerous variables involved don’t allow for a neat Golden Rule chart– the astounding number of possible combinations prohibit such a thing.

You could do an Internet search for your CPU/GPU combination but if your current hardware is mismatched then finding such an article will be difficult. Tech writers tend to post articles about great hardware combinations, not poor ones.

Fortunately, there is a very simple solution and you only need to download one marvelous little tool called FRAPS. (FRAPS is an acronym for “Frames Per Second”.)

fraps-settings-image

FRAPS is a small utility that I have used many times over the years. It is a small, free download that installs in seconds. Here is where you can find it: FRAPS Home Page

What You’ll Do

  1. Download, install, and run FRAPS  (There is online help which describes everything)
  2. After you get the FRAPS settings the way you like (elementary stuff, by the way), fire up your favorite game
  3. Play a while and take note of the Frames Per Second (FPS). The FPS will commonly jump all over the place depending on how much action is taking place. Try to settle on an average throughout your game play. Take note of the maximum and minimum as well.

Note: This is off the top of my head but, if I remember right, anything less than 30fps is going to start looking like a fast slide show instead of a smooth, flowing video image.

In any case, if you are seeing sub-par Frame Rates, lower some of the graphics settings in the game. Anti-aliasing in particular, will cause some big performance hits. Take note of your changes so you can return them to the original status if you need to.

I think the best approach is to avoid changing a whole bunch of things. Just pick one, lower it, and test again. It’s much easier to keep track of things that way.

Now, here’s what you’ve all been waiting for…

  • If lowering the graphics settings has no effect on frame rates, then the bottleneck is your CPU
  • If lowering the graphics settings increases the frame rate, then your GPU is reaching its upper limits

That’s pretty straight-forward, isn’t it?

A Word About Vertical Synchronization (VSYNCH)

VSYNCH may be a setting included within your game settings. It will most certainly be included in your graphics driver settings. I won’t go into technical details, but basically VSYNCH keeps your GPU from sending image frames to your monitor faster than it can display them. There is no worry about physical damage to your monitor, but it may cause a lot of irritating visual ‘tearing’ to occur if VSYNCH is disabled.

The reason I bring this up is that if you have a monitor that runs at 60 cycles per second (Hz), then the maximum frame rate you can expect in games is 60 per second. The same upper limit will match your monitor’s refresh rate whether it be 60, 75, 120 or even higher. The whole point is that I don’t want you to expect 80FPS on a 60Hz monitor. It ain’t gonna happen with VSYNCH enabled.

I turned off VSYNCH in Skyrim one time as an experiment. The frame rates jumped to an unbelievable 120+ on my 60Hz monitor. The quality of the images also tanked so badly that it was unplayable. Man! It was ugly!

Conclusions

Sometimes, the simplest answer can be the most difficult to find on the Internet. I find that a tad odd. This seems to especially occur on forums where you’ll receive all sorts of convoluted answers that may or may not address the original question. I’ve wasted many hours scouring these sites and find it most irritating. Personal experience, commonly known as the school-of-hard-knocks, can be an equally painful and lengthy process.

  • Experiment with VSYNCH. You will cause no damage and disabling it in some games may actually help in your particular situation. This really boils down to whether you can stomach the visual glitches that may occur.
  • If you are the brave type, you might consider overclocking the offending component. Be aware there are risks and you may end up really wishing your were playing a herky-jerky game instead of staring at a Blue Screen of Death on Christmas morning, not to mention a much lighter wallet. Not fun…
  • If you have a terribly slow hard drive and have the extra RAM you might try storing the game’s files on a RAM-Drive. This won’t solve a CPU or GPU bottleneck, but it will most certainly improve scene load times if there is a lot of disk access going on.
  • If the RAM-Drive idea interests you, there are a few articles on that topic right here on DCT that you might enjoy.

There are literally thousands of possible combinations when it comes to computer hardware and I’ve only barely touched one of them.

I wish you all a safe and loving holiday season,
Richard

About the Author

Richard Pedersen

Richard received his first computer, a C-64, in 1982 as a gift and began dabbling in BASIC. He was hooked! His love for computing has led him from the old “XT” boxes to the more modern fare and from clunky 10MB hard drives to smooth and fast modern day SSD drives. He has run BBS services, Fido mail, and even operated his own computer repair business.

34 Comments

  1. Fascinating article Richard.
    Also, as games become more sophisticated and demanding, there also come a point when the entire PC becomes a huge bottleneck.
    Up until 2010 I was running a Pentium 4 3.2 with a 512Mb GPU. As time went on, I added memory up to the max, changed the GPU and HDD, all to squeeze a little more juice out of the poor old thing.
    I think it was when I installed Crysis I realised that it was time to bite the bullet.
    Cheers
    Marc

    • Hi Marc,

      Merry Christmas!

      I have never tried Crysis but I understand it is a demanding piece of software even for modern systems.
      You mentioned that you have maxed out the RAM but don’t say how much that is. These days, I don’t recommend anything less than 4GB on any Windows system.
      Also, a 1GB Graphics card is absolutely the bottom limit– a 2-3GB card is probably advisable for any recent demanding games such as Crysis.
      Given the astounding costs of GPUs these days, purchasing one of these monsters can, in itself, be a demanding task. They can cost as much as many mid-line computers.
      And don’t forget the oft-neglected Power Supply. Without an adequate PSU, nothing will work in a stable manner. Don’t skimp on these.

      Glad you found the article interesting and hopefully useful, too,
      Richard

  2. Merry Christmas to you too Richard!
    I was limited to the max permissible by the board, in this case an Asus P4P800 socket 478, maximum 4 Gb.
    It ran Windows 7 just fine, it has to be said, but in the end the hardware just couldn’t process the increasing demands of the games I was installing.
    And you’re right, Crysis is still a demanding game on very high settings even for a modern quad core.
    I might add that the PC I use at home is a purely gaming machine, which I’ve tweaked to be able to post this message lol.
    I’ll post up my specs sometime if I can find the right area.
    Cheers
    Marc

  3. I have amd fx 8120 with a amd hd radeon 6970 xfx 2gb with 8 gb ddr3 1600
    And from the start of windows 7 on desktop it start to lagging like it has the oldest cpu gpu ram in the world

    • Hi edon,

      Sudden beginnings of lagging can be cause by several things. Malware is one of the first things to check out, especially if slow starts are not the usual for your computer.

      Check out what is in your Start Up folder and eliminate anything you don’t need right off.
      Run a full system scan with your antivirus software.
      Run a full system scan with a dedicated malware scanner such as MalwarBytes or EmsiSoft.

      That should keep you busy for a while,
      Richard

  4. I have an AMD FX 6300 @ 3.5 ghz with stock cooler, soon buying a hyper 212 evo for it so I can try to overclock it on a ASROCK 960GM/U3S3 FX Motherboard. I don’t think it will work but I hope someone can help me out on that.

    The real problem here is my constant stuttering from games. I’ve tried running OpenHardwareMonitor to see what’s underload, and yeah it is quite under load, about 90% on most cpus cores during a sudden fps drop which appears to be a CPU bottleneck. But I’m not entirely sure how to fix it even with a £30 motherboard that I think I think I can’t overclock on.

    Any solutions to this problem? Thanks in advance.

    • Oops, forgot about my build.
      AMD FX 6300 @ 3.5 GHz
      GTX 660 WINDFORCE EDITION
      550W XFX PSU
      8GB CORSAIR RAM
      ASROCK 960GM/U3S3 FX Motherboard

    • Hi iSuckAtGames,

      (I envy your name since it applies to me as well. I wish I’d thought of it.)

      First off, I’d say to forget about any attempts to over-clock (OC). Before OC, get things stable first. Know the limits of your system in its natural state.

      Second, have you tried reducing all the settings in your game to the lowest graphics levels?
      If this helps, you can increase each setting until you find the one that may be causing the stuttering problems. This knowledge will help you focus on the correct approach to “fixing” things.
      Continue “upping” these settings until you find the best ones that still keep the game playable.

      The goal is to find the highest levels that your computer can handle without degrading the playability of the game. Also, give yourself (and your computer) some “wiggle room”.

      Resist the tendency to change more than one setting at a time or you will quickly lose track of your progress.
      Change a setting, play the game a while and if all goes well, bump it up another notch.
      Rinse and repeat.

      (It has been my experience that Anti-aliasing (AA) will have a huge impact on game play issues. I would suggest focusing on that setting first.)

      After that time-consuming task is done, you may then consider some OC tinkering.

      Be sure to make some backups along the way.

      Hope this helps and let us know how it goes for you,
      Richard

  5. If you have a Nvidia card try downloading Nvidia Experience which will detect your system hardware and give you optimal graphics setting setting s with one click. The optimal settings are set to keep you above 40fps – 60fps

  6. Hi richard, recently i just built a new pc. Im not sure if my pc is experiencing bottleneck problem but just sometimes i got a delay, my mouse cursor is moving slow its not happening everytime though. Still i doubt if im having the same problem. My specs are:
    I7-4770K
    8GBRAM
    GTX 970
    Z-97P(motherboard)
    2TB HDD

    Thank you for your reply in advance

    • Hi kenji,

      Awesome specs– you built a nice machine there!

      Mouse lag can sometimes be caused by:

        Too long a USB cable. Check your favorite search engine for maximum recommended lengths
        Mouse settings: Disable Mouse Pointer Trails, Smart Move, and Acceleration in Games
        Keyboard settings: Disable StickyKeys, ToggleKeys and FilterKeys in Control Panel->Keyboard
        Non-essential USB devices– unplug them
        Startup programs– disable the ones you don’t need
        Make certain your motherboard (BIOS) USB settings are correct and not pointing to PS/2 devices that don’t exist
        Try using the default MS mouse drivers instead of the manufacturer’s which can sometimes add a lot of unnecessary overhead
        Make sure you have the latest and greatest GPU drivers particular to your system
        Game settings– Set everything low and bump them up one at a time until you reach your system’s best performance at that level. Time-consuming, I know, but it will certainly give you exquisite insight into what your computer can do.

      There are probably many other reasons for experiencing mouse lag in a game, but this should get you started. From personal experience, I can say the VSynch setting generally makes a difference.

      The very first thing I’d check out are the mouse drivers. Try to stick with the MS default if you can. They are simpler. Of course, by doing so, you may have to sacrifice some of the perquisites associated with the manufacturer’s drivers.

      If any or all of the above does not help, then use your favorite search engine to get some more specific answers related to your system configuration. If you’re having a problem, then chances are in favor that somebody else is, too. The answers are out there…

      Hope this helps,
      Richard

  7. Hi Richard I concerned what on my built will bottleneck. This is not complete yet as I do not have all parts that is why I am asking.
    My build is:
    FX 4100
    16GB of ram
    M5A97 LE R2.0
    500 GB hard drive 7200 rpm
    GTX Titan Black
    PC Power and Cooling MK II 950 Watt

    Should I upgrade the CPU or the CPU and the hard drive to prevent bottlenecking?

    • Hi Zigizigzig,

      Given the sheer number of combinations of CPU and GPU that are possible in our complex world, I can not possibly know in advance which play best together.

      The only valid suggestion I can make is to search the Internet and try to find your answer there. I have had to perform that task in the past and I’m sure somebody has answered your question much better than I possibly can.

      You might start by checking out tech sites for reviews on motherboards, CPUs and GPUs. As you go, take notes of the various combinations of these that were used during their tests. Undoubtedly, you will begin to see an emerging pattern of combinations that seem to work well together. This gleaned information should get you started in the right direction towards making an educated decision for building your own system.

      Good luck and if you find a solid answer, please let us know,
      Richard

    • Don’t buy those components. The CPU you have chosen is a low end CPU and the GPU is one of the best on the market. Go for a better CPU and a lower spec GPU. A GPU I recommend is the GTX 970 and for CPU it’s up to you. If you drop the Titan and get a GTX 970 you can afford to get a much better CPU.

  8. Hey Richard, I just ordered a new pc to play some games
    which has cpu=Core i5-3340 3.1GHz,
    and gpu=GeForce GT 640 Asus 2GB DDR3 Edition
    and 8Gb RAM
    (prices are very high in my country i couldn’t afford higher specs :/)
    i would like to know if the gpu would bottleneck the cpu?

    • Hi Herro,

      I can’t personally answer any bottleneck questions for specific components. My experience is limited to my own machines and I have no means of testing all the possible combinations.

      The best I can do is suggest you search “GT640 bottleneck i5 3340” using your favorite search engine. You will get lots of hits.

      Hope this helps,
      Richard

  9. Thanks for the answer Richard, I searched what you said in many possible ways and couldnt find anything.And i even searched for cases where gpu bottlenecking cpu but barely found any case of this happening. Like can you give me an example or something if you find any or tell me how does it happen?

    • Hi Herro,

      I just did this search on Bing and got 7 hits; the same search on Google offered over 7000.

      Granted, the results aren’t necessarily identical to the search parameters, but by reading the ones that are close and narrowing down the best answers you can find, it should give you a pretty good idea of where your system stands.

      You may have to spend a lot of time doing this but it all depends on how important the answer is to you. You’ll certainly have a definitive answer when your start running games on your new computer.

      Hope this helps,
      Richard

  10. Thanks for your answer Richard and im definitely going to search for more information.I’m getting the pc in a few days i’ll be posting if i have any problems.
    Have a good day 🙂

  11. Hello All,

    With Assassin’s Creed Unity here and Dragon Age Inquisition on the way I’ve been considering upgrading my graphics card. Problem is its been so long that I don’t know which card to get. Bottle necking is something that I have considered since my PC is old.

    Build Specs:
    Intel core i7 930 @ 2.80 GHz
    12 GB RAM
    Antec 750 watt PSU
    XFX Radeon HD 5770 with 1GB of RAM
    ASUS P6T SE Mother Board

  12. Hi! after reading this article, I finally realized about the meaning of bottlenecked CPU&GPU and I think I’m one of those people. I need your advice thou. I recently bough a new CPU: AMD A10 6800K APU processor, A88XM-P33 Mobo, 8GB Kingstopn Hyper X RAM, Truerated HUNTKEY PSU 600W and 1 TB WD. I was playing like GTA IV and Prototype but FPS were very low. I already lowered the graphics but it keeps lagging. I’m not sure if it will resolve the issue since based on the reviews that I’ve read that. IF IT DOES WORK, what GPU will I buy, I read that R9 290x is good enough?? please help. Thank you.

    • Hey Jude (sorry, I couldn’t resist),

      The first thing that jumps out at me is the APU. And I don’t see you mentioning a graphics card.

      For the likes of GTA, and other graphically demanding games, I don’t think an APU is the answer.

      A Quality GPU – Consider dipping into the old light-sensitive wallet (George Washington squints when I open mine) and get yourself a proper graphics card. The R9 200 series is outstanding and I’m sure it will meet your desires. Be prepared for a little Sticker Shock, though. You get what you pay for, usually. Sometimes, you pay for what you get :-/

      Check out the online reviews for various cards and decide which one suits your purposes in the best way. I like “Tom’s Hardware” and “PCPer” for this purpose. There are some very knowledgeable people working at these sites who generally offer more information than you might care to know.

      My Stuff – My gaming preference is turn-based strategy/simulation games. They are not nearly as demanding as first-person shooters, but since installing an R9 280X, I am able to run the likes of Skyrim and Civ V at the highest settings. This card doesn’t begin to snort. It consistently runs at about 45% load at these settings. I am very happy with this card.

      A Good PSU – Keep in mind that cards of this caliber do require considerable amounts of stable power. The keyword here is “stable”. Cheap PSUs are the bane of quality gaming systems. A 600W PSU may be at the bare-bones lower limit. And if it is a “discount” PSU, the problem only gets worse. Keep in mind that these top-notch cards can heat a small room. They are power-sucking vampires of the electronic variety.
      Others who have much more experience than I may be able to offer better suggestions in this regard.
      Marc, speak up! 🙂

      The Latest Drivers – Visit your MoBo manufacturer’s site for the latest drivers and follow their installation instructions to the letter.

      VSynch – One thing you might try in the interim is disabling VSynch. If you can tolerate the possible resulting “tearing” effect, it may improve your FPS and any mouse-lag that you might be experiencing. You have nothing to lose by trying… if it doesn’t work, revert.

      I hope this helps and Good Luck to you,
      Richard

  13. I’d be interested to know if Jude is running the graphics off the APU only or his Radeon 5770, which in its time was a very worthy card.
    Many GPU’s specify a minimum requirement of 500W or above, which in itself is a tad vague. As an example, I’m running a Radeon 7950 which needs two 8 pin pcie power connectors, with each sucking up 75W, so a ‘min spec’ of 500W isn’t going to cut it and 650W with, as Richard points out, a clean stable supply, should give you many hours of happy gaming.
    Get back to us on the graphic output please Jude.

  14. Hi again! @Richard Pedersen (I knew you would notice my name haha!!) Anyways, Tom’s Hardware is really somethin’ in terms knowledge based (Thumbs up!!) That’s where I got the idea of the precised GPU that I think will suite my CPU. I read it from there that R9 270X 2GB DDR5 256 Bit will resolve the issue. (That’s what they say on that forum). My question is, do I have to get more than 2GB of GPU so that it can overpower the iGPU of A10 6800K? or will it suffice if I choose R9 270x 2GB instead? I was thinking of buying AMD FX series in order to gain better GPU. But that will be the near future I suppose. *Sigh T_T

    • Hey Jude,

      Tom’s Hardware is certainly a go-to site. A great place to visit.

      As with all things, more memory is better. (That includes old men like me. and my hard disk is full 🙁 A lot of swapping going on…)

      If your wallet can stand the strain, I would opt for more RAM on the GPU. My card has 3GB RAM and doesn’t get entirely used when playing a huge map in Civ V. That tells me that all the textures are being stored on the GPU and are therefore nearly instantaneously available.
      I definitely noticed the improvement when I upgraded from a 2GB card. That doesn’t display the full picture however, because the new card is faster, too.

      I have no experience with APUs. My first inclination would be to disable the graphics side of that processor, if that’s even possible. Don’t take my word for it, though. Do some research. Maybe some kind person will comment on this thought right here? Or maybe you already know the answer to this question? 😉

      Ultimately, speed is what we’re after here. Just get the biggest, fastest card you can afford. Be sure your PSU and MoBo will support it.

      More RAM will inch you in that direction,
      Richard

  15. Okay Thanks for the helpful tips!! really do appreciate it. I’ll go with your advises. I’ll save up some money then buy the R9 270X. I’ll keep you posted once I tested it. Thanks again.