Technology
The product today was developed by ATI under the codename R420 and is of course lined up against the mighty nVIDIA 6800 series, they manage to compete very well for sure. The x800 XT graphics core is built on a 0.13-micron fabrication process with no less than 160 Million transistors. As you know there are two x800 products available in retail, the Pro version has 12 pixel pipelines as opposed to its bigger XT brother with 16. Make no mistake, both products have the exact same core yet the Pro version has 4 pixel pipelines disabled, which cuts down performance by ~25%. The VPU furthermore has two pixel shader units per pipeline, the pipes are organized into four groups of four, six vertex shader units, four-way crossbar memory controller and at default should have a 450 MHz DDR-3 memory frequency.

I've placed an overview of the competing products in this chart:

	nVidia GeForce 6800 Ultra	ATI Radeon X800 XT	ATI Radeon X800 Pro	ATI Radeon 9800 XT
Transistor Count	220 million	160 million	160 million	110 million
Manufacturing Process	0.13-micron	0.13-micron, low-k dielectric	0.13-micron, low-k dielectric	0.15-micron
Core Clock Speed	400MHz	520MHz	475MHz	413MHz
Pixel Pipes	16	16	12	8
Texturing Units	16	16	12	8
Vertex Pipelines	6	6	6	4
Memory Interface	256-bit	256-bit	256-bit	256-bit
Memory Clock Speed	1.1GHz DDR-3	1.1GHz DDR-3	900MHz DDR-3	730MHz DDR-2
Peak Memory Bandwidth	35.2GB/sec	35.8GB/sec	28.8GB/sec	23.4GB/sec

As opposed to the GeForce 6 series, ATI did not choose to support Shader Model 3 but is compatible up-to model 2.0b, this actually saves them quite a few transistors making the graphics core less expensive. The lack of Shader model 3 has widely been debated, personally I would have loved to see it included on the x800 series, current games however hardly support it just yet (with the exception of Far Cry with the v1.2 patch). Differences will be mostly seen in performance increases. There will be several titles coming out that support Shader Model 3, among them are: Lord of the Rings; Battle for Middle-Earth, Stalker, Vampire: Bloodlines, Splinter Cell X, Driver 3, Grafan, Painkiller and much more...

ATi Radeon x800 Pro & XT