Emulator

The best place to see this is at the start of a game where the wiimote warning comes up. The warning fades in and fades out. Both times the slowdown is there and also in any in game fades.

Running the binary in 32bit and it is still slow?

Please see this topic: http://forums.dolphin-emu.com/thread-10708.html it appears to be the same issue. It contains process samples.

This problem is definitely OSX-specific. In my case, I tried Animal Crossing and the bug occurred during the name select dialog. I can also confirm that it happens when playing Paper Mario.

It seems that the emulator suddenly starts doing LOADS of system calls. The CPU time becomes 99% system. Sure enough, the process samples reflect this.

This should probably get a higher priority since it practically breaks a lot of games on Mac OS X. This is something that happens routinely in games, and it's basically a show stopper.

Does this still happen?

I'll update my sources and recompile later today.

I see this issue on Linux using OpenGL -- in R25EWR, any time a rendered cutscene fades to or from black, FPS slows to single digits. As soon as the fade ends, the FPS snaps back to normal speed.