We should mention, Silicon Optix has released the HQV high-definition video benchmarking discs to the public in general. For Tom's Hardware readers specifically, Silicon Optix gave us promotional codes that take $5 off of the purchase price of the HD DVD and Blu-ray Benchmarks: "TOMSHQVBR" for the Blu-ray benchmark, and "TOMSHQVHD" for the HD DVD benchmark. You can find out more at www.hqv.com.

Measuring the CPU usage during HD video playback is a very relevant test, as HD video eats bandwidth and CPU cycles like nobody's business. The fact of the matter is that older, single-core CPUs that were considered pretty good only a year ago might not be up to the task of simply playing an HD DVD or Blu-ray disk.

Both Nvidia and ATI are promoting their graphics cards as premium playback devices for HD video. While their top tier cards like the Geforce 8800 and Radeon 2900 series have video acceleration built in, it's the new midrange cards like Nvidia's 8500 and 8600 series that are supposed to take almost the entire load off of the CPU when HD video is being played.

There are two main codecs used in HD DVD and Blu-ray disks: the older VC-1 codec, and the newer H.264 codec. VC-1 is the simpler of the two and is therefore easier for the PC to decode. Newer titles use the H.264 codec, which requires much more work to decode, and will bring many modern CPUs to their knees.

The Nvidia representatives we talked to were excited to let us know about how their new 8500 /8600 series cards would allow users of old hardware to view demanding new H.264 video on their machines. This is a bold claim and we're interested to see if it's true. (on a side note, ATI's upcoming midrange cards - the 2400/2600 series - are also supposed to remove the HD video decoding load from the CPU.)

Let's see how hard the CPU will work when we play HD video with both the VC-1 and H.264 codecs on Windows XP and Windows Vista.

The VC-1 Codec in Windows XP and Windows Vista:

Below we'll look at the CPU utilization when a VC-1 title was played on various video cards using both Windows XP and Windows Vista.

We should note that Nvidia reps told us that the advanced video decoding features of the newer 8500/8600 series cards are currently enabled only in Windows Vista at this time, but will be exposed in Windows XP in the future. In addition, ATI reps told us that we should expect similar results from both the X1900 XTX and HD 2900 XT cards.

In Windows XP, we see that ATI's Radeon cards do not seem to accelerate the video decoding task at all, as their results are virtually identical to the non-accelerated results.