I've been in the dev and homebrew scene for awhile now under various names, but recently, a bunch of us have started work on a Xbox emulator for the PSP.
Most of you are probably thinking that I'm speaking out of my ***, but no it's true.
The XBOX hardware is superior to the PSP's CPU, but in terms of the media engine, the capabilities are somewhat similar. Also, by having the emulator automatically tone down GFX effects together with the resolution, we're aiming for a playable framerate.... even for CPU intensive games such as HALO. Now, game size is another concern... considering most XBOX games begin at around the 3 gig mark...
We've been working on totally stripped down rips at the moment... like back in the days of BBS's and FTP's.... cutting out all the music and cutscenes.
Anyway, at the moment, the framerate is around 0.2fps (haha) and although sound effects are heard, as you can imagine, are totally choppy. We're hoping to improve this... so stay tuned, and I'll post more as we work on this.