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A CPU bottleneck happens when the processor cannot prepare frames fast enough for the graphics card, so the GPU waits and runs below full load. The quickest check: if your GPU usage stays below about 90–95% in a game while one or more CPU cores are near 100%, you are CPU-bottlenecked. If GPU usage is at 95–100%, the GPU is the limit, which is normal and expected.
What is a bottleneck in a PC?
Every frame in a game passes through two stages. The CPU handles game logic, physics, AI and draw calls, then hands the work to the GPU, which renders the image. Your frame rate is set by whichever part is slower. That slower part is the bottleneck. Every PC has one, so the goal is not to remove it but to make sure it is where you want it, usually on the GPU.
For the basics of what each chip does, see CPU vs GPU: what is the difference.
CPU bottleneck vs GPU bottleneck
| Sign | CPU bottleneck | GPU bottleneck |
|---|---|---|
| GPU usage | Below 90%, often fluctuating | 95–100% |
| CPU usage | One or more threads near 100% | Usually below 80% |
| Lowering resolution | FPS barely changes | FPS goes up a lot |
| Typical situation | 1080p, high refresh, strategy and open-world games | 1440p and 4K, ray tracing, ultra settings |
| Feels like | Stutter, low 1% lows, uneven frame times | Smooth but lower average FPS |
How to check for a CPU bottleneck
Method 1: Watch GPU usage in game
- Install MSI Afterburner with RivaTuner, or use the NVIDIA app overlay (Alt + R) or the AMD Adrenalin overlay (Ctrl + Shift + O).
- Show GPU usage, CPU usage per core and FPS.
- Play a busy scene for a few minutes without an FPS cap or V-Sync.
- If GPU usage stays well below 95%, the CPU (or a frame cap) is holding the GPU back.
Overall CPU usage can be misleading. A game may max out one or two threads while total CPU usage shows only 40%, so look at per-core usage.
Method 2: The resolution test
Lower the resolution or turn on upscaling at the performance setting. If FPS rises a lot, you were GPU-bound. If FPS stays almost the same, the CPU is the limit.
Method 3: Use Intel PresentMon
Intel PresentMon is a free tool that works with NVIDIA, AMD and Intel GPUs. Its GPU Busy metric shows how long the GPU actually worked on each frame. If GPU Busy is much lower than the total frame time, the GPU is waiting on the CPU.
Are bottleneck calculators accurate?
No. Online bottleneck calculators give one percentage for a CPU and GPU pair, but real bottlenecks depend on the game, the resolution, the settings and your refresh rate. The same PC can be CPU-bound in Counter-Strike 2 at 1080p and GPU-bound in Cyberpunk 2077 at 4K. Testing your own games with the methods above is far more reliable.
What causes a CPU bottleneck?
- An older or low-core CPU paired with a fast new GPU.
- Low resolution with a high refresh rate: 1080p at 240 Hz needs many more frames from the CPU.
- CPU-heavy games: strategy, simulation, MMO and large open-world games.
- Slow or single-channel RAM: one memory stick, or XMP/EXPO turned off.
- Background apps: browsers, launchers, recording and antivirus scans.
- CPU thermal throttling: a hot CPU lowers its clock speed.
How to fix a CPU bottleneck
- Raise the resolution or graphics settings. This moves more work to the GPU, often at no FPS cost when you are CPU-bound.
- Lower CPU-heavy settings: crowd density, view distance, physics and shadow distance.
- Turn on XMP or EXPO in the BIOS and use two RAM sticks in dual-channel.
- Close background apps and turn off overlays you do not need.
- Use frame generation (DLSS Frame Generation or FSR Frame Generation), which adds frames without extra CPU work.
- Cap your FPS slightly below your refresh rate for smoother frame times.
- Update the BIOS, chipset drivers and GPU drivers. See how to update GPU drivers.
- Upgrade the CPU if it is several generations older than the GPU. CPUs with large cache, such as AMD X3D chips, help most in CPU-bound games.
How to fix a GPU bottleneck
A GPU bottleneck is normal, but if your FPS is too low you can lower resolution or settings, use DLSS, FSR or XeSS upscaling, overclock the GPU slightly, or upgrade the card. Compare cards in our GPU performance chart. If GPU usage is high when it should not be, read why is my GPU usage so high.
FAQ
Is a CPU bottleneck bad?
It is not harmful to your hardware. It only means you are not getting the full performance of your GPU.
Is a 10% bottleneck bad?
A small bottleneck is normal and not worth worrying about. Focus on whether your FPS and frame times are good in the games you play.
Can a bottleneck damage my PC?
No. A bottleneck affects performance only, not the health of the CPU or GPU.
Does higher resolution reduce CPU bottleneck?
Yes. Higher resolution adds work for the GPU but not for the CPU, so the GPU becomes the limit.
Is 100% CPU usage a bottleneck?
Often, yes, especially if GPU usage drops below 90% at the same time. Check per-core usage too, since a single maxed thread can cause a bottleneck.
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