I've taken a look at the sources... there is no problem with xnu from 10.5.5 leo but latest xnu seems to be hardly rewritten.. so it will take a while before we see working x64 kernel... though everything seems to be clear. and i don't understand why voodoo team denied from making native x64 for amd... there is only one comment in the sources about that... that after release 1 of voodoo they decided to make only force64 with arch=i386 but not arch=x86_64... :\