The flagship of ATI's expansive product lineup is called RADEON 9800 XT, a derivative of the original R300 with a few notable additions. To begin, it features a new VPU, or video processing unit, internally referred to as R360. Architecturally, it closely resembles the R350, manufactured on a 0.15-micron process and featuring 115 million transistors. The RADEON 9800 XT core runs 32MHz faster than its predecessor, for a total of 412MHz.

Further, onboard memory has jumped from 128MB to 256MB, effectively running at 730MHz and capable of delivering up to 23.3GB per second of bandwidth over the card's 256-bit memory bus.

Even though the 9800 XT's improvements seem conservative, the core and memory together dissipate more heat than the old cooling solution could handle. Therefore, ATI implemented a heatsink and fan combination built entirely of copper.

The top of the card sports a copper plate, covered with rolled copper fins, and topped by a plastic cover that serves as ducting. Meanwhile, the bottom features another slab of copper intended to absorb heat from memory modules mounted back there. Compared to previous cooling solutions from ATI, this one is beefy, but isn't intrusive. The RADEON 9800 XT continues to occupy a single slot, and while the included fan is bigger than ever, it is rigged to run dynamically. That is, an onboard thermocouple actively determines the core's temperature and adjusts fan speed accordingly. It's hardly audible in a 2D environment.

The obvious reason for an integrated thermocouple is to monitor onboard temperatures. However, an interesting side effect is that the card knows when it is running either cooly or entirely too fast.

Thus, beginning with the CATALYST 3.8 driver set, ATI includes a software feature called OVERDRIVE that serves as a form of sanctioned overclocking. For as long as the RADEON 9800 XT operates within a given thermal range, it will run at higher frequencies.

For example, at 50 degrees Celsius, OVERDRIVE sets the card to its maximum setting, 432MHz. As the card heats up, its core frequency drops to 419MHz, and finally in an extreme case, back to the stock setting of 412MHz.

Overclocking the Sapphire

Just because OVERDRIVE is able to dynamically overclock the 9800 XT doesn't mean it is the most effective tool for the job. In fact, given the results of our own overclocking tests, OVERDRIVE seems relatively ineffective at reaching really good speeds.

If you'd like to experiment with a slightly more aggressive utility, Sapphire bundles its own Redline software, based on Rage3D Tweak. With it, we were able to hit some incredible speeds, though in order to ensure stability, we settled on 471MHz for the core and an effective memory clock of 808MHz.

At those enhanced frequencies, the Sapphire 9800 XT demonstrates a roughly 10 percent improvement in 3DMark03 (cough, cough), jumping from 6466 3DMarks to 7085. The Unreal Tournament 2003 'Flyby' demo picked up closer 12 percent, and the 'Botmatch' demo gained three percent, both at 1600x1200.