> I've read every 8.1 and HFS+ -related post in the Mac newsgroups, and have
> not seen an answer as to why a 68k system cannot boot from a HFS+ volume.
> They do put a wrapper around it so that if one boots from a system < 8.1,
> all they'll see is a file with a message explaining that you need 8.1 to
> use the volume.  Maybe it's something about that wrapper that messes up 68k?

Well, think about how the machine boots. The ROMs have routines that search
the disks for an HFS volume and then run through the HFS volume to find the
system file. The ROMs then load the system file and run the system.

The ROMs in the 68k macs were designed only with HFS in mind. The PowerMacs
have more flexible booting procedures. Good example: when I use linux-pmac
I can boot straight out of Open Firmware into Linux from an ext2fs parition.

It might be possible for 68k Macs to boot using HFS+ if HFS+ supports boot
sectors. If it does then bootstrap HFS+ code could be put into the bootsector.
When the ROMs found the partition, they would load the bootsector code and
run it to find where the system file was.

However, there are problems with that idea. Most notably, if the HFS+ paritions
are not labeled as straight HFS paritions then the ROMs most likely skip them
when searching for bootable partitions. Worse still, there are security and
virus related problems to this sort of booting procedure.

The "must have HFS parition" thing is really what keeps us from having a
true bootloader on 68k macs. The closest we could get might be a fake HFS
parition with a long bootsector or an HFS partition with bootstrap code
contained in a "fake" system file. Either way, you can't have a system
without at least one drive that's partitioned Mac style with at least one
HFS parition on it (or at least one floppy disk :-) )