> For G5 there has to be a fix applied so the JIT will be working.

I think the JIT is already working on G5, just that some instructions might not suit the G5 too well and are thus executed rather slowly. http://tenfourfox.blogspot.com/search/label/ppc970 has more information on general instructional differences between G5 and G3/G4.

Edit:

"“Mcrxr” is toxic on G5 cpu's, so I looked for it in EUAE, and there are few references too it, maybe this what causing slow down?"
http://www.amigans.net/modules/xforum/viewtopic.php?post_id=85905#forumpost85905

From Fab:
"sysinfo indicates about 85mips on a 2.3 GHz G5, which is rather ok (it's a private build that doesn't try to use the slow mcrxr instruction). [...] The released OS4 build is not "optimal" for G5 or PA6. It performs horribly when the mcrxr instruction is used."
http://amigaworld.net/modules/newbb/viewtopic.php?topic_id=29062&forum=27&start=160#726602

From Rachy (the JIT author):
"G5 needs a special version, which was compiled using a define. One of the PPC instructions is not availavle on G5, so it triggers an exception and it is handled by the OS."
http://amigaworld.net/modules/newbb/viewtopic.php?topic_id=29062&forum=27&start=180#726674