ATi Radeon X800 XT PCIe

by John Reynolds

Introduction

The old adage, “if it’s not broke, don’t fix it,” comes to mind with ATi’s Radeon X800 graphics boards. When ATi released the 9700 Pro in the fall of 2002 using a 150nm process, the world-and more importantly for the company, their competition — was taken by surprise. The R300 architecture, upon which the 9700 Pro was based, was a DX9 compliant part that used floating point precision throughout its rendering pipelines, a design that wasn’t thought possible by most of the industry if using the older fabrication process. Yet this is exactly what ATi accomplished, introducing the first DX9 graphics chip months ahead of competing parts, and moreover outperforming the competition once it arrived significantly later. In fact, ATi obviously felt so confident in their new architecture that they have continued to essentially leave the core technology unchanged for several refreshes throughout 2003 and for this year’s new generation, the X800 series of products. This has allowed ATi to instead focus engineering resources on a new architecture that will be powering both Microsoft’s Xbox 2 console and the company’s next generation of graphics boards for the PC.

Announced this past May, the Radeon X800 product series consists of the X800 Pro, the X800 XT, and theX800 XT PE (Platinum Edition). Based on the R420 architecture (R423 for PCIe versions), these chips are 160m transistor parts manufactured using TSMC’s 130nm low-k process and have a 256-bit memory interface that supports DDR, GDDR2, and GDDR3. To diversify the X800 product line so that it can address multiple price points in the market, ATi has created the following board specifications:

The R300 was the first graphics chip on the market to feature eight pixel pipelines, and ATi has continued this parallelism by doubling the number of pipes for the R420 and increasing the vertex engine from four to six units. Yet while there are chip and memory speed variations among the X800 lineup, the most noteworthy difference is the X800 Pro’s 12 pipelines as opposed to the other boards’ 16 pipes. Essentially the same chip as the XT and XT PE but with one block, or quad, of pipelines disabled, the Pro’s configuration results in a significantly lower fill-rate. The boards themselves offer ATi’s typical output options, with single VGA and DVI connections and an S-video port. And thanks to the use of TSMC’s low-k process, the X800s are single slot boards that can be installed in small form factor PCs and cooled using a copper heatsink and fairly quiet fan (the speed for which is controlled by an on-die thermal probe that monitors the chip’s temperature and adjusts its rotation accordingly). In fact, the 256 MB of GDDR3 memory that ATi uses for these new cards does not require active cooling, so the heatsink doesn’t actually make contact with the RAM modules (four on the front and back each) on the board.

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