What Does Fill Rate Mean?
Fill rate refers to the number of pixels that a video card can render or write to memory every second. It is measured in megapixels or gigapixels per second, which is obtained by multiplying the clock frequency of the graphics processing unit (GPU) by the number of raster operations (ROPs). GPUs with higher fill rates are able to display video at higher resolutions and frame rates compared to GPUs with lower fill rates.
There is no standard for calculating and reporting the fill rate, so companies have come up with their own ways of calculating it. Some multiply the clock frequency by the number of texture units, while others multiply the frequency by the number of pixel pipelines. Whatever the method, the calculation produces a theoretical value that may or may not fully represent real-world performance.