To celebrate the 11th anniversary of the US release of the SEGA Dreamcast, the folks over at the PSO Archive have released the beta versions of two ambitious titles that were in development at one time for the console - Irrational Games' System Shock 2 and Looking Glass Studios' Thief II. It doesn't sound like they're fully playable in their current state, but the team is hoping that someone out there will be able to get them up and running in a proper state for another future release. The games clock in at several hundred megabytes each, which you'll discover by jumping straight to the download directory here.