Windows XP CPU utilization
Since many enthusiasts have balked at moving to Windows Vista, we threw the cards through a quick round of CPU utilization tests in Windows XP. Here, we can enjoy the full benefits of DirectSound hardware acceleration without Vista's Universal Audio Architecture getting in the way.

The Xonar DX looks remarkably good here, managing lower CPU utilization than even the hardware-accelerated X-Fi. Something's not quite right about these results, though. The Xonar D2X's CPU utilization was much higher with a previous driver revision, and with DirectSound 3D GX offloading positional audio calculations onto the host CPU, it shouldn't be using fewer CPU cycles than the X-Fi.

Since the ability to encode multi-channel audio over S/PDIF is a key feature of the Xonar DX, we've run some RightMark 3D Sound tests with digital output. For these tests, the Xonar D2X, X-Fi XtremeMusic, and ALC889A were configured to pass DTS Interactive bitstreams. The Xonar DX can't output DTS Interactive, so it was set to use Dolby Digital Live instead.

Switching to multi-channel digital output doesn't change the picture much. The ALC889A's CPU utilization rises slightly, but the Xonar handles Dolby Digital Live with aplomb.

Power consumption
Power consumption has become a staple of our hardware coverage here at TR, but it's not something we usually tackle with sound cards. Normal sound cards don't come with auxiliary power connectors, though, so we busted out our Watts Up? Pro power meter and measured total system power consumption, sans monitor and speakers, at the wall outlet. Systems were tested at idle and again while playing an MP3.

The Xonar DX consumes marginally less power than the D2X, and a little more than the X-Fi. Note that adding a discrete sound card doesn't increase overall system power consumption by all that much over integrated motherboard audio.