Can some one explain pixel processors

[yan816]

Hi, I am looking at getting a new graphics card and have been out of the loop for a while. So can some one explain what the difference is beteween having either 48 or 36 pixel processors?

[chuckskull]

Pipelines, to put it brutally simply, more is better. Usually the lower number is a cut down version of a faster card.

[kalniel]

*nods* Pixel shaders are used for more programmable effects, such as refractions, accurate lighting etc. Rather than have a hard coded effect that can be directly accelerated by a chip in the card, effects can now be functions/equations that more generalised processors solve for each pixel. This requires quite a bit of work, and it also scales up badly (a higher resolution equals more pixels which means more number crunching).

This quickly became rather hard to accelerate by just increasing the speed of one processor, so gfx cards started using lots of processors in parallel. 36 or 48 is the number of small shader processors that a card has, and as it's a relatively parallel proceedure, it more or less directly relates to the speed of a card in processing pixel shaders.

Of course, a card has to do more than just pixel shading, so it's not the be all and end all, and NVidia and ATI have different strategies in this respect. ATI have gone for a high shader count compared to the rest of the other card components, giving good performance in shader heavy games like Oblivion. NVidia on the other had have a more conservative number of shaders, but aim for a higher total through put and texture processing capabilities, resulting in better performance in texture heavy (and co-incidentally openGL) games.

[yan816]

Thanks for the reply kalniel , That would explain why each card is better in some games than the other. Now all I have to do is decide what card to replace my X850XT with.

[maverick77_uk]

But with DX10 cards and the *rumours* that there are going to be unified shaders in the GF8800 allowing the card to pick and choose whether that pipeline is a pixel or vertex shader depending on demand AND maybe 128 of those....things get interesting......!