The 360 version matches the PC's 60 FPS while the PS3's framerate runs at just 20-30 FPS. "The PS3 does lag a little bit behind in terms of getting the performance out of it," Carmack acknowledges.
"The rasteriser is just a little bit slower - no two ways about that. The RSX is slower than what we have in the 360. Processing wise, the main CPU is about the same, but the 360 makes it easier to split things off, and that's where a lot of the work has been, splitting it all into jobs on the PS3."
He is, however, confident that the PS3 version will match that of all other supported platforms: "Everything is designed as a 60 hertz game. We expect this to be 60 hertz on every supported platform."
"The work remaining is getting it locked so there's never a dropped frame or a tear, but we're confident that we're going to get that."