Microsoft this week announced it would offer an HD-DVD drive as a peripheral to the Xbox 360 before the end of the year. But don't expect to see any 360 games using this format any time soon.

Chris Satchell, general manager at Microsoft's game developer group, says the HD-DVD drive is going to be for playing back HD-DVD movies only. "We're not using [HD-DVD] for game development," he said.

Xbox games, he says, will continue to be on DVD-9 media (dual-layer 8.5GB DVDs). This is because Xbox 360 games are hitting 720p – as opposed to 1,920x1,080 for maximum-resolution HD (high-definition) content.

"DVD-9 is continuing to supply sufficient space for storing the content of these games," says Satchell. "720p is our sweet spot for next-generation rendering techniques – for the lighting, the shadows, the surfaces. That's the sweet spot for the number of pixels to render to, and that's where the GPU is targeted."

This is not to say you'll never see the drive operate as a means to play Xbox 360 games, though. "We've made Xbox 360 a future-proof system," Satchell explains. "We can make decisions to modify the system if developers are interested in that."

For playing back movies, the Xbox 360 will max out at 1,080i output. You'll need the Xbox 360 Component HD AV cable, which connects via the unit's audio/video port.