>If this Partition gets damamged and the disk is the primary boot disk, 
>the Mac ROM will abort the boot process with Death Chimes even *BEFORE* 
>allowing one to boot off the floppy!  Having done this to myself when I 
>was working on mkfs I decided not to inflict the same harsh lesson on 
>others by not "fixing" the Partition Map off-by-one error in mkfs.  Maybe 
>that wasn't the right decision, but it seemed correct at the time.

I should have pointed out when I wrote this the reason for changing the 
way mkfs uses the Partition Map.  In Mkfs 1.2 the Partition Map was only 
read, never written, so going off the end never really was too serious.  
In mkfs 1.4 we now have the ability to "zap" MacOS Partitions into NetBSD 
type partitions.  To do this the corresponding Partition Map entry block 
needs to be re-written.  Writing a block on the the disk's SCSI Driver 
Partition because of a bad Partition Map is a real possibility and in 
fact happened once to me during testing.  Making mkfs work with Partition 
Map entries that are known to be valid was an easy way of protecting 
against this error.

Hope this clears things up a bit,
-bob