X700 architecture

X700 PRO and GeForce 6600 GT

Board design is similar on both X700 cards

In case you aren’t up to date with the core architecture of ATI’s RADEON X700 chip, we’ll provide a quick refresher of the VPU and the underlying cards that are based on it.

Like GeForce 6600, the RADEON X700 is based on a 0.11-micron manufacturing process manufactured by TSMC. This is important, as the smaller 0.11 micron process allows ATI to cram 40% more transistors per unit area than the previous process, 0.13-micron, freeing ATI to add more features into the graphics core without having to resort to a larger, more expensive to produce chip.

ATI uses this to integrate more pipelines into X700 – eight pixel pipelines with one texture unit per pixel pipeline. This is the same pipeline configuration ATI used on their high-end RADEON 9700 and RADEON 9800 last year, so ATI is essentially moving this technology down to the mainstream segment. X700 goes one step further than RADEON 9700/9800 by integrating six vertex units, two more than the four vertex units that were used on 9700/9800. X700 also supports the more robust 2.0b pixel shader specification, which adds support for longer pixel shader programs, and more instructions (1,536 versus 160 previously), and finally, X700 also features support for ATI’s 3Dc normal map compression.

In order to keep costs down, one high-end feature that’s typically found on high-end cards, a 256-bit memory interface, was axed from X700. Instead, the X700 relies on a more conventional 128-bit memory interface, featuring dual 64-bit memory controllers.

The cards

ATI offers three different cards that are based on X700 technology, all share the same basic feature set, with the only differences being performance and price. At the top of the X700 lineup is the X700 XT. The X700 XT features a 475MHz graphics core while the memory operates at 525MHz. This provides a texel fill rate of 3.8Gigatexels/second, a figure which is better than the RADEON 9800 XT by 14%. Memory bandwidth peaks at 16 Gigabytes/second.

Two different X700 XT SKUs are offered: a 128MB card, and a 256MB variant. The 128MB X700 XT retails for $199, while the 256MB card goes for $249. In our past testing, we’ve found that newer titles such as Far Cry and Half-Life 2 both benefit from the extra memory, so if you can spare the extra $50, it may not be a bad idea to opt for the 256MB card.

Size comparison between 6600 GT and X700 PRO

Too bad X700 PRO AGP cards havent been released yet

With copper cooling, the X700 XT is the heaviest of the mainstream cards

If you’re in the market for a less expensive 256MB card, the midrange X700 offering is the X700 PRO. The X700 PRO features a slower 420MHz core clock frequency, while its memory operates at 432MHz. It retails for $199.

At the bottom of the X700 lineup is the RADEON X700. X700 ships with the same core features as the other cards, including the 8 pixel pipes and 128-bit memory interface, only with slower clocks. ATI has committed to 400MHz on the graphics core and 300MHz DDR1 memory (600MHz effective). These are the same clocks as RADEON 9600 PRO/X600, but thanks to the boards 8 pipeline configuration, the X700 should offer dramatically more performance when it ships and will be priced at an MSRP of $149.

All X700 cards will initially support PCI Express, just like the GeForce 6600. To serve the existing AGP add-in card market, ATI also plans to ship AGP-based X700 cards, but these cards won’t hit retail until later this year. Since the X700 supports PCI Express natively, ATI will have to integrate a bridge chip on their AGP X700s.