> Since I installed a 1.0A kernel (and rebuilt the entire user land,
   > which built without problems) I get into the kernel debugger upon reboot
   > from MS-DOG (i.e.: ctrl-alt-del and then select NetBSD from my osbs20b8
   > boot menu).

   Yes, I had exactly the same problem (486/33, 8 Mb, 2 IDE drives). I have not
   seen it since I rebuilt, on  Dec 1st, but then again, I have not (re)booted
   the machine often since then, and the problem doesn't always appear.

In /sys/i386/i386/locore.s, change:

	pushfl
	popl	%eax
	andl	$~(PSL_AC|PSL_ID),%eax
	pushl	%eax
	popfl

to:

	pushl	$PSL_MBO
	popfl

and see if you still have that problem.