MorphOS is API and binary (ABI) compatible with AOS 3.x (barring couple of things, such as BCPL).
MorphOS started as a tight microkernel + static (no just-in-time compilation back then) 68k emulator for PowerUP cards. Only couple of core components were PPC native back then (exec, expansion and couple of other things). The KS ROM components were replaced one by one with PPC native versions, but the 68k APIs were kept. This way any OS legal 68k app will continue to run as it has no idea how the actual underlying OS function is implemented.
The obvious benefit of using the 68k emulation is that you don't need to worry about the caches. With dual 68k and PPC you must manually keep track of caches and flush when needed. This results in severe penalties as typically both 68k and PPC caches are fully flushed when switching the processor.
Also, once you throw in JIT compilation, the emulated 68k runs circles around 68060, not to mention 68040@25.
W00T, this was my 4000th post.
