Texturing fill-rate

Very often a company suddenly pops up numbers that are way higher than the number you would expect from the Theoretical Peak fill-rate Definition. When the fill-rate number you see is too high then chances are pretty high that the number quoted is a Texturing fill-rate and not a Theoretical Peak fill-rate.

The Texturing fill-rate is defined as the number of texels used for rendering during one second. The calculation is very similar to the previous one : you take the clock speed of the 3D chip and you multiply it with the number of texture units, then you multiply that number with the number of texels that is used by a single texturing unit.

Again this might sound cryptic but an example with make it clear:

Originally the ATI Rage 128 GL processor was designed to run at 125 MHz. The Chip has two rendering pipelines (same as texture units). Each pipeline can render a bi-linear filtered on-screen pixel per clock. For Bi-linear filtering you need four texels. The Texturing fill-rate is thus : 125 (clock) x 2 (pipelines/units) x 4 (texels) = 1000 Mtexels or 1 GigaTexel/sec.

This is the definition used in the following quote:

" ATI introduces next-generation RAGE 128 GL graphics chip delivering world's best performance and features to the high-performance PC Market ... First to break the 1 Gigatexel per second texturing barrier with SuperScalar rendering engine and single-pass multi-texturing ... "

Unfortunately many people got confused after this press release because they believed that the number quoted was a Theoretical Peak fill-rate number. I personally don't think this fill-rate-definition should be used since its only purpose is to trick and deceive people. Naturally the higher number is extremely tempting for Marketing People. So when you see a number that is much higher than that of the competition, and when very little details are provided then be on your guard because the number quoted is probably a Texturing fill-rate and not a Theoretical Peak fill-rate.

For example the Voodoo 3500 processor running at 188 MHz with 2 texturing units each using bi-linear filtering has a Texturing fill-rate of 188 x 2 x 4 = 1504 Mtexels or 1.5 GigaTexels/sec. This number reduces the huge impact made by the high number quoted by ATI.

Note that Texturing fill-rates are always expressed in Mtexels and never Mpixels.