Elite Bastards podted a review on the Club 3D Radeon X1900 XTX video card

So, what's different about R580? A couple of things as it happens, the major focus being the amount of pixel shading power on offer. R580 has grown to a total of 384 million transistors, over 60 million more than the 321 million found on the R520 core with which it shares its 90nm manufacturing process.

Those sixty million transistors or so have largely been spent on tripling the number of pixel shader units in R580. Whereas R520 features sixteen pixel pipelines (four pixel quads), each containing a single pixel shader unit, R580 again features sixteen pixel pipelines, but this time each of these contains three pixel shader units, making for a total of 48 inside the core. If this sounds at all familiar to you, it's because we've already seen a similar configuration on ATI's RV530 part, aka the Radeon X1600. On that occasion, we saw a core utilising four pixel pipelines (a single quad of pixels) each with three shader units, giving a total of twelve shader units. R580 simply repeats this configuration on a grander scale - Indeed, come the launch of the Radeon X1000 series, the boards handed out by ATI to most developers were not Radeon X1800 parts, but rather X1600 boards, to prepare them for the shift in emphasis that R580 would bring.

Club 3D Radeon X1900 XTX - R580 Unleashed