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ATI's new AGP Radeons

A bridge is born

ALTHOUGH PCI EXPRESS is undoubtedly the future of PC graphics, AGP isn't nearly dead yet. In fact, since PCI Express platforms have only been available for about a year—or around five months if you favor the Athlon 64—AGP still has a massive installed base among mainstream consumers, gamers, and even PC enthusiasts. At least some of those users are going to want graphics card upgrade options that don't involve a motherboard swap, so it's no surprise that ATI recently spiced up its AGP Radeon family.

For a little over a year, ATI's Radeon X800 series GPUs have powered the company's high-end AGP offerings. Over that time, however, ATI has introduced a number of new graphics products, including the Radeon X850 XT PE that boasts dynamic clock gating and higher clock speeds than previous Platinum Editions, and the Radeon X800 XL built with 0.11-micron fabrication technology. For months, these new graphics cards were limited to PCI Express, but AGP versions of each have recently become available. ATI has also bolstered its AGP lineup with the addition of an All-in-Wonder Radeon X800 XT. Together, these cards breathe new life into a graphics interface that's been largely ignored for the last six months, but are they any good? Let's have a look.

The cards
The first and perhaps most interesting addition to ATI's AGP lineup is the Radeon X800 XL. The X800 XL has already proven itself a potent performer for PCI Express, so we're happy to see it migrating to AGP. What makes the X800 XL particularly interesting is the fact that its graphics chip is built using 0.11-micron fabrication technology. Well, that and its sixteen pixel pipelines running at 400MHz for about $300, but I digress. You can read more about the Radeon X800 XL's graphics chip in our review of its PCI Express counterpart.

ATI's Radeon X800 XL AGP reference card

Physically, the Radeon X800 XL AGP card is huge. At nearly nine inches long, it's the largest ATI graphics card we've ever had in the labs. Note that the card also sports a four-pin Molex connector; a PCI Express x16 slot has enough juice to power the X800 XL on its own, but the AGP version of the card needs a little help.

ATI's answer to HSI

The AGP version of the X800 XL actually uses a native PCI Express graphics chip in conjunction with an ATI bridge chip translating PCI Express commands to AGP. NVIDIA does something similar with the GeForce 6600 GT AGP, which uses the company's High Speed Interconnect (HSI) bridge chip as a middleman between the PCI-E graphics chip and AGP interface. The ATI chip runs without a heat sink, though, while NVIDIA's HSI bridge requires passive cooling.

You'd think ATI would be eager to use its newly developed bridge chip on more graphics cards, but it's nowhere to be found on the AGP version of the Radeon X850 XT Platinum Edition. ATI hasn't even snuck the silicon onto the graphics chip's packaging, suggesting that the company has developed a native AGP version of its R480 GPU.

The Radeon X850 XT Platinum Edition AGP card

Like the Radeon X800 XL, the X850 XT Platinum Edition's GPU serves up a sweet sixteen pixel pipelines, but this time they're running at 540MHz. That makes this card an absolute fill rate monster, and with GDDR3 running at an effective 1.18GHz, the X850 XT PE has gobs of memory bandwidth, as well. However, the X850 XT PE's most interesting feature isn't its peak theoretical performance. The card also has Pentium M-esque dynamic clock gating capabilities, which allows it to turn off inactive portions of the chip. Dynamic clock gating allows the chip to run cooler and consume less power at idle, and when coupled with a temperature-controlled fan, it can also lead to lower noise levels. You can read more about the Radeon X850 XT PE's graphics chip in our initial review of the X850 series.

Before moving on, we should note that unlike its PCI Express counterpart, the AGP Radeon X850 XT Platinum Edition lacks dual DVI outputs. That's particularly disappointing considering that the card sells for over $400.

An All-in-Wonderful Radeon X800 XT

The third entry in our AGP sweepstakes is the All-in-Wonder X800 XT. You won't find any fancy new GPUs or bridge chips here, just an All-in-Wonder version of ATI's existing Radeon X800 XT. The AIW X800 XT is currently the fastest member of ATI's All-in-Wonder lineup, and with NVIDIA's Personal Cinema all but dead, it doesn't really have any single-card competition. We'll only be looking at gaming performance and power consumption today, but stay tuned for more in-depth coverage of the card's video handling features in an upcoming article.