I've just learned something that compels me to publish a major correction to our review of the Radeon HD 2900 XT GPU. I got the clear, distinct impression from AMD's presentations, statements, and conversations with me at its Radeon HD press event that its new UVD video decode acceleration logic was present in its entire lineup of Radeon HD graphics chips, and I relayed that information to you in our review of the product, promising to follow up with tests of this feature at a later date.
True to my word, I set out yesterday to test HD video decode acceleration on a Radeon HD 2900 XT using an HD DVD drive and a version of PowerDVD supplied by AMD for such purposes. To my surprise, CPU utilization during playback on our Core 2 Extreme X6800 test system ran between 40 and 50%, well above what one would expect from a solution with full HD video decode acceleration.
Naturally, I contacted AMD to inquire about the problem. I received a reply from AMD's David Baumann discussing the issue that ended with this revelation:
"Be aware, though, that HD 2900 XT itself does not feature UVD, this is specific to 2600 and 2400, so the levels of CPU utilization you see should be somewhat similar to the previous generation. "
The UVD logic handles the CPU-intensive bitstream processing and entropy decode acceleration portions of the HD video playback pipeline. These are the most notable video decode acceleration capabilities that would separate the Radeon HD 2900 series from its direct competition, the GeForce 8800 series, if the HD 2900 XT actually had them. Turns out it does not. As the email states, the video playback capabilities of the Radeon HD 2900 XT are essentially similar to those of the previous-gen Radeon X1950.