High-end video card releases have traditionally been comprised of new architectures coupled with increased clock speeds, with any one option coming to the fore depending on the R&D schedule. ATI has been at the forefront of this technology race, and with the exceptional R300 and R350 cores, provided a virtually unbeatable combination of features, performance and image quality. The latest ATI high-end product used the new R360 core, and while the Radeon 9800 XT did follow previous designs and allowed higher-than Radeon 9800 Pro clock speeds, ATI also gave us something new.
This was referred to as ATI OverDrive technology, and basically occupied a side-panel in their white papers that described an automatic overclocking feature built into the Radeon 9800 XT cards. Upon release, this option was not available, but with the introduction of the Catalyst 3.8 drivers, the OD feature became part of the default driver package. To enable it, simply check the OverDrive box on the driver tab and you're off. We're here to run the ATI Radeon 9800 XT through the paces, and to see exactly how this new OverDrive technology affects overall 3D game performance.
The Radeon 9800 XT ships at defaults of 412 MHz core and 730 MHz DDR memory clock speeds, and the ATI OverDrive feature extends this even further (up to a 460 MHz core speed, according ATI white papers). This is an automatic, on-demand overclocking technology that uses variables such as core and case temperature, GPU load, etc. and provides automatic core speed increases. This is different than constant overclock settings, as the ATI drivers actively monitor and adjust core speeds due to the above-mentioned variables, and there is no facility to permanently select a set speed. We've used the SUV analogy before, but it still fits quite well, and ATI's OverDrive is quite similar to on-demand 4-wheel drive, where the feature enables when needed, but cannot be directly controlled.
The design of the ATI OverDrive feature also means there could be a slight difference in overall performance depending on the operating environment and the game testing performed. We made every attempt to emulate a well-cooled, high-end desktop system, ensured that the GPU was adequately ventilated, and took a short break between tests. Of course, the ATI Radeon 9800 XT was put through the ringer afterwards, and while we didn't find any stability problems, long-term usage of high-end 3D games can result in slightly lower benchmark scores.