My FPS starts around 300 when I begin a League of Legends match, but gradually falls to about 170 and drops below 100 after 20–30 minutes. During the slowdown, CPU usage stays below roughly 50% and GPU usage is only around 5–20%. Temperatures appear to be normal. What could cause this kind of performance degradation, and what should I check?
3 Answers
Low GPU usage is expected if the game is limited by a single CPU thread or another system bottleneck. Total CPU usage can still look low because the other cores are mostly idle. Compare per-core CPU usage and clock speeds during the match, and check whether anything in the background gradually consumes resources or causes the game client to slow down.
The most likely possibilities are thermal or power throttling, even if overall CPU usage looks low. Check the CPU and GPU temperatures, clock speeds, and temperatures of individual CPU cores while the FPS is falling. You should also provide your full PC specifications, including the CPU cooler, graphics card, RAM, and power settings, since low utilization alone doesn't identify the bottleneck.
There isn't enough hardware or software information to diagnose it confidently. List the CPU, GPU, RAM, cooling setup, operating system, graphics settings, and whether the FPS drop also affects other games. Monitoring temperatures, per-core utilization, clocks, RAM usage, and background processes while the issue occurs should help narrow it down.
I checked the temperatures and they look normal. The game is League of Legends, but I haven't listed my full hardware specs yet.