CPU & GPU Bottleneck Explained
A PC bottleneck occurs when one component in your system limits the performance of another, preventing both from reaching their full potential. In gaming, CPU and GPU bottlenecks are the most common — a poorly-matched pair can reduce your frame rate by 20–40% compared to an optimally-balanced build at the same budget (Source: Hardware Unboxed, paired build testing 2024). Use our free Bottleneck Calculator to check how well-matched your CPU and GPU are.
Types of PC Bottlenecks
Bottlenecks aren't limited to CPU and GPU — every component in a PC can become the weakest link under specific workloads. Here are the four most common types gamers encounter:
| Type | Fix |
|---|---|
| CPU bottleneck | Upgrade CPU, reduce CPU-heavy settings (LOD, NPC density, physics) |
| GPU bottleneck | This is ideal; lower resolution or quality if FPS is insufficient |
| RAM bottleneck | Add more RAM; enable dual-channel (install in correct slots) |
| Storage bottleneck | Upgrade to NVMe SSD; enable DirectStorage (Windows 11) |
How to Check for a CPU Bottleneck
The most direct method is monitoring both CPU and GPU usage simultaneously while gaming. Use MSI Afterburner (free) with RivaTuner Statistics Server to display an on-screen overlay showing real-time percentages.
A CPU bottleneck shows as CPU utilisation above 90% on all cores, with GPU utilisation stuck below 80% — and a frame rate lower than your GPU's spec should deliver. This means the CPU is completing game logic and draw calls slower than the GPU can render them.
Games most sensitive to CPU performance include: city-building games (large unit counts), open-world RPGs (NPC simulation density), and competitive shooters at very high frame rates (200+ FPS) where per-frame CPU work becomes the limiting factor. Use our Refresh Rate Test to confirm your monitor is actually running at its full rated Hz before diagnosing a bottleneck.
CPU vs GPU Bottleneck: Which Is Worse?
A GPU bottleneck is actually the desired state. When your GPU runs at 95–100% utilisation, every shader core is being used — you are extracting maximum value from your graphics card. The frame rate you see is the maximum your GPU can produce at your current settings.
A CPU bottleneck is the problematic scenario. It means your GPU is sitting partially idle (60–80% utilisation) because the CPU can't supply draw calls fast enough. Upgrading your GPU in this situation would provide no improvement — the new GPU would idle at the same percentage.
The resolution test: if lowering your game resolution from 1440p to 1080p significantly increases your frame rate, you have a GPU bottleneck (expected). If lowering resolution barely changes FPS, you have a CPU bottleneck — the GPU was already underutilised. To see how your overall system performance translates to real-world gameplay, try our Reaction Time Test — high CPU bottleneck often manifests as inconsistent frame pacing that hurts your measurable reaction window.
How to Fix a CPU Bottleneck
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Reduce CPU-bound in-game settings
Simulation quality, NPC/vehicle density, draw distance, and physics quality are all CPU-heavy. Lowering these frees up CPU headroom without affecting visual quality as much as reducing GPU settings.
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Increase resolution or quality
Counter-intuitively, increasing graphics resolution shifts more workload to the GPU — which helps if your GPU is underutilised due to CPU bottleneck. At 4K, GPU work dominates; CPU bottlenecks are far less common than at 1080p.
- 🔧
Enable XMP/EXPO for RAM
Memory speed directly affects CPU bandwidth. Enable XMP (Intel) or EXPO (AMD) in BIOS to run your RAM at its rated speed. Many systems ship with RAM running at 2133 MHz even if the kit is rated for 3600 MHz — a 20–30% performance gain in CPU-bound scenarios.
- 🖥️
Upgrade the CPU
If the above don't resolve the bottleneck, a CPU upgrade may be necessary. Use our Bottleneck Calculator to find CPU/GPU pairings within your budget that reduce the bottleneck percentage.
Frequently Asked Questions
What is a PC bottleneck?
A PC bottleneck occurs when one component in your system cannot keep up with the demand generated by another, limiting overall performance. In gaming, a CPU bottleneck means your processor is too slow to feed frame instructions to the GPU fast enough. A GPU bottleneck means your graphics card cannot render frames fast enough, regardless of how fast the CPU runs. Some bottleneck is always present — the goal is to keep it under 10–15%.
How do I know if my CPU or GPU is bottlenecking?
Open Task Manager or MSI Afterburner/HWiNFO while gaming. Check GPU utilisation first: if it's consistently at 95–100%, your GPU is working at full capacity — this is ideal and means your CPU is keeping up. If GPU utilisation is 60–80% and your FPS is lower than expected, your CPU may be bottlenecking. A CPU bottleneck shows as high CPU usage (90–100%) with GPU usage well below 100%.
Is 100% GPU usage a bottleneck?
No — 100% GPU usage is actually the ideal state. It means your GPU is fully utilised and is the performance-limiting factor, which is exactly what you want in a GPU-bound workload like gaming. A GPU bottleneck only becomes a problem if your CPU is idle (low usage) while your GPU is maxed out and your target frame rate is not being met.
What percentage bottleneck is acceptable?
A 10–15% bottleneck is generally considered acceptable — it means the slower component is within 10–15% of the faster one's pace. A bottleneck over 30% will noticeably hurt performance. The 'perfect' pairing has ~5% bottleneck. Use our Bottleneck Calculator to check how well-matched your specific CPU and GPU combination is.
Does RAM affect bottleneck?
Yes. Insufficient RAM or slow RAM can cause a CPU bottleneck independent of the processor itself. For gaming in 2025, 16 GB DDR4 at 3200 MHz is the minimum recommended. Running in single-channel mode (one stick instead of two) halves your memory bandwidth and can significantly bottleneck the CPU, especially in games sensitive to memory speed like Cyberpunk 2077 or Hogwarts Legacy.
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