With the new Xbox 360 dashboard out around the world today, more people are installing games to their hard drives. And more people are noticing that Halo 3 actually takes longer to load when played from a hard drive than it does when running from the DVD. The Bungie blog updated this morning with a brief technical breakdown of the hows and whys behind Halo 3's performance.
The piece is a Q&A with Bungie's Mat Noguchi, who describes how Halo 3 uses the hard drive under normal circumstances. It seems that it already caches the maps to the hard drive for faster loading, even when you're playing from a disc. When you're running the game from the hard drive, it then has to copy those maps from one spot on the hard drive to the temporary utility partition used for cached data.
In short, reading and writing using the same device takes longer than moving that data from the disc to the hard drive.
Check out the full post for a bit more technical detail. For what it's worth, Bungie says that it will continue to monitor the situation, but says that fixing these new issues require a significant effort on their part and that it "could really be a rather significant change."
Considering how much I'm enjoying the newly quiet 360 when it's running off the disc, I'd probably consider installing Halo 3 anyway, even if the load times are a bit longer. But then, I haven't played Halo 3 is a pretty long time and probably won't pick it back up anytime soon.