A CPU vs GPU bottleneck comes down to one question: in the game you're playing, is the processor or the graphics card the part that stops the frame rate going higher? Every gaming PC has a limit in every game, so having a bottleneck isn't a fault. What matters is whether it's the one you expected, and whether it's holding you below the frame rate you want. Knowing which it is stops you spending money on the wrong upgrade.
What is a bottleneck in a gaming PC?
A bottleneck is the part that's working flat out while the others wait for it. To draw each frame, the processor works out what's happening in the game, the physics, the AI and what needs drawing, then hands that to the graphics card to render. If the processor can prepare 150 frames a second but the graphics card can only render 90, you get 90 and the card is the limit. Swap those numbers and the processor is the limit.
In most games at 1440p or 4K with high settings, the graphics card is the limit, and that's how a well-balanced gaming PC should behave. A processor limit is more common in fast competitive games at 1080p, in strategy and simulation games, and in big open-world games with lots going on. The same PC can be limited by its graphics card in one game and its processor in the next.
How can you tell if your CPU or GPU is the bottleneck?
Watch the graphics card's usage while you play: if it sits at 95 to 100 percent, the card is the limit, and if it's well below that, the processor or something else is. You can see it with the overlay in MSI Afterburner, or with the performance overlays built into the NVIDIA and AMD apps. Play normally for a few minutes, in a busy part of the game rather than a menu.
Then confirm it with a resolution test:
- Note your frame rate in a repeatable spot, like the same stretch of a level or a built-in benchmark.
- Drop the resolution or the render scale a step or two, leaving every other setting alone.
- Run the same spot again and compare.
If the frame rate jumps, the graphics card was the limit, because you gave it less to do and it went faster. If the frame rate barely moves, the processor was the limit, because it was already feeding the card as fast as it could.
| What you see | Likely limit |
|---|---|
| GPU usage at 95 to 100 percent | Graphics card |
| GPU usage well under 90 percent, frame rate below what you want | Processor, memory or a frame cap |
| Lowering the resolution raises FPS a lot | Graphics card |
| Lowering the resolution barely changes FPS | Processor |
| Both CPU and GPU usage low, frame rate still poor | Frame cap, V-Sync, heat or a fault |
Why doesn't total CPU usage tell you much?
Because games rarely use every core evenly, so a processor can be the limit while Task Manager shows it at 40 percent. Most games have one or two main threads that do the heavy lifting. If those threads are maxed out, the game is processor-limited, even though the other cores are idling. Monitoring tools that show per-core or per-thread usage give a truer picture, but the GPU usage and resolution tests above are simpler and more reliable.
What can catch you out when testing?
A few settings cap your frame rate on purpose, and they make both parts look under-used:
- V-Sync or a frame cap: if the frame rate sits exactly on 60, 144 or another round number, a cap is doing its job. Turn it off while testing.
- Heat: a processor or card that's overheating slows itself down, which can look like a bottleneck.
- Memory settings: RAM running at its base speed, or a single stick, can hold back the processor in games.
- Upscaling: DLSS, FSR and XeSS render at a lower resolution, so turn them off or leave them alone while comparing.
What should you upgrade if the CPU or the GPU is the limit?
If the graphics card is the limit and you're happy with the frame rate, there's nothing to fix. If you want more, lower a demanding setting or turn on upscaling first, and look at a new card when that isn't enough. A new card often needs more from your power supply, so check that before you buy.
If the processor is the limit, you have free headroom on the graphics card: raise the resolution or quality settings and you'll often lose very few frames. Make sure the memory profile is switched on. Beyond that, a faster processor is the fix, and on an older PC that can mean a new motherboard and memory too. Our post on whether to upgrade or rebuild an older gaming PC walks through that decision.
For a quicker answer, try our bottleneck checker. Answer five quick questions about what's bothering you and how old your parts are, and it suggests which upgrade to look at first. If you'd like it checked in person, we can test your PC in our Midland workshop and fit the right part.