| I have OpenFirmware on my machine (PowerMacintosh G4).  As I see it,
| the bootloader (and the kernel, which it chains to) are just gigantic
| subroutines called by OF.  Therefore, the kernel ought to be able to
| return to OF as the result of some flavor of cpu_reboot, with things
| set up so that I could continue using OF (all CLAIMed memory freed,
| etc.)

Sure.  When you halt a SPARC it returns to the firmware.  However,
if you try to boot some other kernel, the firmware is intelligent and
resets itself.  So in theory there's no reason you couldn't at least
return to the `ok' prompt.

In practice, the kernel has probably changed the configuration of
important devices, so the firmware may not be able to deal with that.

Eduardo