Fill rate
Fill rate is how many pixels or texels a GPU can write per second, setting a hard ceiling on performance at high resolutions and with heavy overdraw.
Also known as pixel fill rate, texel fill rate, ROP throughput
Not measurable from a browser
A browser cannot read temperatures, power draw, fan speed, VRAM capacity, clock frequency or native FLOPS. For a direct reading use a native monitor such as HWiNFO64, GPU-Z or lm-sensors. SystemCheck contributes the other half: whether the condition is costing you throughput, measured as decay and consistency.
Pixel fill rate is ROP count times clock; texel fill rate is texture-unit count times clock. Both are ceilings on the back end of the pipeline. Fill rate mattered enormously in the fixed-function era and matters less now that shading dominates, but it still bites in specific cases.
Those cases are high resolution, heavy overdraw from stacked transparency, and particle-dense scenes where the same pixels are written many times. A card that runs a game comfortably at 1440p and falls apart at 4K with heavy alpha effects is often fill-limited rather than shader-limited.
SystemCheck's raster stage applies calibrated pressure that includes fill work, so a fill-rate limitation shows up as elevated frame times under that load. SystemCheck does not report fill rate as a separate number (it cannot read ROP counts or clocks from a browser). It reports the frame-time consequence.
Related terms