ATI Radeon X1800 XT


With prices for natural gas and home-heating oil spiraling out of control, upgraders looking for a hot new videocard will want to take a look at ATI’s new Radeon X1800 XT. This card generates so much heat it could replace a small furnace.

OK, we’re exaggerating. But the X1800 XT really does get warm. In spite of its high temperature, the X1800 XT is clearly superior to ATI’s previous top-of-the-line part. For starters, the entire X1000 series finally supports Microsoft’s Shader Model 3.0. This development should dissolve any reluctance game developers have had about embracing Shader Model 3.0, which should result in more visually sophisticated games hitting the market.

ATI tells us its decision to manufacture the X1000 series of GPUs using a 90nm process enabled a dramatic increase in core clock speeds: the X1800 XT runs at a staggering 625MHz, compared with the Radeon X850 XT Platinum Edition’s 547MHz core, and the 430MHz core on a stock GeForce 7800 GTX. But what’s really astounding is the fact that ATI has cranked the clock on the memory to a blistering 750MHz.

When we re-viewed nVidia’s GeForce 7800 GTX back in our September issue, we quipped that “24 is the new 16, when it comes to pixel pipelines.” ATI must not have gotten that memo, because the Radeon X1800 XT features only 16 pixel pipes. But then, perhaps it’s not the number of pipes, but what a GPU does with those pipes that really matters. (Or maybe it’s simply a matter of driving the whole enchilada at unheard-of clock speeds.)

ATI offers the X1800 XT with two memory configurations: 256MB for $500 and the $550, 512MB version reviewed here. When the 512MB version of the X800 XL shipped a few months back, ATI reps told us game developers were chomping at the bit to gain access to larger frame buffers. Although we’re skeptical of that claim, the $50 price delta separating the 256- and 512MB versions is a smokin’ deal.

ATI’s new “ring bus” memory controller—a third feature common to the X1000 series—is almost more interesting than the GPU’s process size. Rumors that had ATI’s new GPUs boasting a 512-bit memory architecture were only half right: As implemented in the X1800 cards, the memory controller is surrounded by two 256-bit rings. Data from read and write operations runs in opposite directions around these rings, arriving at ring “stops” (one for each pair of memory channels) that are linked directly to the chip’s memory interface. ATI maintains that this design enabled an increase to memory clock speeds while simultaneously reducing latency. Be that as it may, GDDR3 memory is GDDR3 memory, so we’ll be watching closely to see if ATI can actually acquire enough 750MHz chips to satisfy demand.

So what about performance? In our game benchmarks, the X1800 XT edged past XFX’s GeForce 7800 GTX on four out of seven tests. Fans of Doom 3 (and Quake 4, and all the other games that will be based on that engine), however, will want to consider this card’s poor showing with that game. Aside from the disappointing Doom 3 score, the card performs well. If ATI can do this well with just 16 pipes, imagine what it could have done with a 24- or 32-pipe processor.

We’re severely disappointed with this card’s video performance: ATI seems to have taken one step forward and a step-and-a-half back. The step forward is color saturation that’s clearly superior to that of both ATI’s previous-generation cards and nVidia’s latest offering. The HQV composite score of 51, on the other hand, is 14 points lower than what ATI’s X850 XT Platinum Edition earned in the videocard roundup we published in November (and it’s a whopping 32 points lower than that of the 7800 GTX). What happened? The X1800 XT actually performed dramatically better on most of these benchmark tests—including jaggies compensation and 3:2 pull-down detection—but when it came to the film-cadence tests, ATI’s new card failed every test except one.

As for the rest of ATI’s much-hyped Avivo video technology, we’re left wondering if it’s a lot of smoke and mirrors, or if ATI just hasn’t finished implementing everything in its device driver. At the time of this review, ATI told us that only two DVD-player programs—Cyberlink’s PowerDVD and Intervideo’s WinDVD Platinum—were capable of fully tapping the X1800 XT; and even then, both players required Registry tweaks. Microsoft’s Windows Media Player, we were told, still had “issues” with hardware acceleration at high resolution.

The X1800 XT is a promising card for games, but in light of its disappointing video performance, coupled with the fact that CrossFire Edition versions of the card weren’t available at press time, it’s difficult for us to get very excited about it right now.
Michael Brown

Month Reviewed: December 2005

+ MEXICAN VANILLA : Slightly faster than a single nVidia GeForce 7800 GTX

- MEXICAN PRISON : Intensely hot card requires a two-slot cooler; lousy video performance; no CrossFire Edition (yet).

Verdict: 8

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