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Re: CVS commit: src/sys/arch/x68k/stand/boot_ustar

On Tue, Apr 15, 2014 at 12:43:42PM -0700, Dennis Ferguson wrote:
> I'm pretty sure NetBSD could never run on a 68000 since the 68000
> had no memory management unit.  The 68010 and 68020 didn't have memory
> management units either, but Sun did proprietary MMUs for both (that's
> sun2 and sun3, respectively) and I think other companies may have done
> MMUs for the 68020.  The 68030 was the first CPU in the series to come
> with an MMU built in.

ISTR that either (or both) of the 68000 or 68010 don't save enough
state to make all address faults recoverable.
This stops you running OS that do paging - so you could only run
OS that swap entire processes.

The '020 saves the mid-instruction state for some faults (as well as the
actual fault reason) so they can be recovered.
(Just don't continue on a cpu with a different mask level.)


David Laight:

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