XENOS Demystified @ Beyond3D

Posted on the front page by Rys:

Dave Baumann, EIC over at Beyond3D, who's sat opposite me swearing at his laptop in a Canadian hotel, has just activated his analysis of the graphics hardware in XBOX360. Codenamed C1 by ATI and more commonly known as XENOS, the 3D hardware in Microsoft's new console is a radical departure from current PC 3D hardware in the way it processes tris and processes and pushes pixels.

In simple terms, an array of arithmetic units that can process vertex or pixel data, before outputting to a unified memory architecture via an off-die eDRAM and ROP processing package, C1 is the most advanced and capable graphics processor ever created. Here's a snippet.

With its unified shader pipeline Xenos has a fundamental difference with virtually all current shader capable graphics processors and whilst shader processing are enveloping both the geometry and raster pipeline, until now they have done both those elements distinctly. On Xenos there is a logical disconnect between the old OpenGL pipeline, which is basically the evolution path most graphics processors followed, as now the geometry and pixel shader processing are moved on to a single processing element of the chip as all the shader ALU's can dynamically be tasked with either vertex shader programs or pixel shader programs.

Check it out in full over here. It's a fairly technical read, so put your 3D hat on if you dare to venture into the analysis of what'll draw the images on the new XBOX.

But, the question is Wheres Thomas?

Is that an in-joke, or have I lost the plot? You better not be starting with the in-jokes!

8 pixel writes per cycle, so this is like a 500 Mhz r300 but with free 4xFSAA and with those 8 pixels having a lot more shading done on them before being shoved out to the screen. And where r300 might only be 60-70% efficient and so not capable always of putting out 8 pixels in that cycle r500 manages 90% or so.

Would that be a good summary ?

Regards

Andy

In terms of pixel processing, that's pretty tenuous. That it can only write out 8 pixels per clock via the ROP hardware is the only real connection to R300.

R500/C1/XENOS can texture from the vertex hardware, filter float textures, multi-sample float rendertargets and all kinds of stuff R300 (or anything up to R420) can't. Never mind the fact there's more than 12 times the ALU power at the same clocks.

The architecture is a radical departure from ATI's recent PC hardware, so it doesn't make that much sense to compare them like that.