CPU-bound
A workload is CPU-bound when the processor cannot feed the GPU fast enough, so frame rate stops rising even though GPU utilisation stays below 100%.
Also known as CPU limited, CPU bottleneck
Measured by SystemCheck
Part of the four-stage run: a 60-second sustained CPU load reporting throughput, decay and consistency; a memory stage reporting bandwidth and latency; a calibrated GPU raster load reporting frame time, pacing and decay; and a path tracer reporting samples per second. The paragraphs below say which metric carries this term.
The signature is unmistakable once you know it: GPU utilisation sits at 60-80%, CPU shows one or more threads pinned, and lowering graphics settings changes nothing. The GPU is idle waiting for work that the CPU has not finished preparing.
Causes include heavy game simulation, large numbers of draw calls, driver overhead on older APIs, and single-thread limits in engines that cannot spread their critical path. It is most common at low resolutions and high refresh targets, where the GPU finishes each frame quickly and spends the rest of the interval waiting.
The fixes follow from the cause: raising resolution or settings moves the limit back to the GPU, reducing crowd or draw-distance settings cuts CPU work directly, and a faster CPU or faster memory raises the ceiling. SystemCheck's CPU stage measures your processor's sustained multi-core capability, which tells you whether that ceiling is your chip's design or your machine throttling below it.
Related terms