Unfortunately there's no writeup or such about it, but I worked on a doomed (ha!) project to port Unreal 1 to PSX. I was doing level design at the time. The pro

Unfortunately there's no writeup or such about it, but I worked on a doomed (ha!) project to port Unreal 1 to PSX. I was doing level design at the time. The programmers did manage to get a functioning renderer up. It was limited to more simple geometry than the PC software renderer could handle at the time, but still worked enough you could have made a game on it, had other things not gone wrong with the project. If you search for "Unreal PSX" you'll find some work by a couple diehard retro unreal fans to try to finish up some of the partially completed content.