The Pro product has 12 pixel pipelines opposed to it's bigger XT brother with 16. Make no mistake, both products have the same core yet the Pro version has 4 pipes disabled. I already noticed some interesting soft and hardmods on the web to enable these extra 4 pipes.

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 400-550 MHz DDR-3 memory. See any differences with the 6800 here? No? Good... as indeed it's the same. Differences need to be found in transistor count, architecture and the core frequency and memory bandwidth mostly.

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

Opposed to the GeForce 6 series ATI did not choose to support Shader Model 3 but uses 2.0b. This is being hotly debated, personally I would have loved to see it included on the x800 series, current games however do not support it just yet and whether or not it'll make a visual difference can be questioned. Differences will be mostly in performance increases. There will be a few titles out supporting Shader Model 3 among them Lord of the Rings; Battle for Middle-Earth, Stalker, Vampire: Bloodlines, Splinter Cell X, Driver 3, Grafan, Painkiller, Far Cry and more...

ATi Radeon x800 XT