@thomas
1)
The 680x0 JIT emulator (Petunia) thats built in to OS4 emulates the 680x0 faster then a real 680x0 CPU, programs are also highly accelerated by OS4 native system files, when they are used.
http://www.amiga.hu/amigos/rachy/petunia.html2)
Emulating the 680x0 CPU eradicates the need for context switches between to two CPU's, the result is no cpu cache flushes needed, the need for cpu cache flushes needed was always a problem whit WarpUP/PowerUP in the past, and has always resulted in slow downs, when ever AmigaOS3 communicated whit WarpUP OS.
3)
It's a shame that Petunia can not be used in UAE, because it does not support offset addresses as required by UAE.