Driver overhead
Driver overhead is the CPU work required to translate rendering commands into GPU instructions, which can bottleneck a fast GPU paired with a slower CPU.
Also known as CPU driver overhead, API overhead
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.
Every draw call passes through the graphics driver, which validates state, manages memory, and builds command buffers. That work runs on the CPU. Older APIs such as DirectX 11 and OpenGL do much of it on a single thread, so a draw-call-heavy title can be CPU-limited by the driver itself even when the GPU is idle.
Vendors differ measurably here, and the effect scales inversely with CPU strength, which is why a GPU comparison run on a high-end CPU at 1080p can rank cards differently than the same comparison run on a mid-range CPU. Modern low-overhead APIs (Vulkan, DirectX 12, WebGPU) reduce but do not eliminate the cost.
In the browser the overhead stack is deeper still: your JavaScript, the browser's graphics process, ANGLE translation on Windows, then the native driver. SystemCheck's GPU results therefore include browser overhead and sit below native-API numbers for the same card. WebGPU generally shows lower overhead than WebGL2, which is why SystemCheck reports the backend it used. A WebGL2 result and a WebGPU result are not directly comparable.
Related terms