Fillrate

The term pixel fillrate refers to the number of pixels a video card can render to screen and write to video memory in a second or in case of texture fillrate the number of texture map elements (texels) GPU can map to pixels in a second. Pixel fillrates are given in megapixels per second or in gigapixels per second (in the case of newer cards), and they are obtained by multiplying the number of Raster Output Units (ROPs) by the clock frequency of the graphics processor unit (GPU) of a video card and texture fillrate is obtained by multiplying the number of Texture Mapping Units (TMUs) by by the clock frequency of the graphics processing unit (GPU). Texture fillrates are given in mega or gigatexels per second. However, there is no full agreement on how to calculate and report fillrates. Other possible method is: to multiply the number of pixel pipelines by the clock frequency. The results of these multiplications correspond to a theoretical number. The actual fillrate depends on many other factors. In the past, the fillrate has been used as an indicator of performance by video card manufacturers such as ATI and NVIDIA, however, the importance of the fillrate as a measurement of performance has declined as the bottleneck in graphics applications has shifted. For example, today, the number and speed of unified shader processing units has gained attention.