Message-ID: <98@redwood.UUCP>
Date: Fri, 14-Dec-84 04:43:51 EST
Article-I.D.: redwood.98
Posted: Fri Dec 14 04:43:51 1984
Date-Received: Mon, 17-Dec-84 03:19:28 EST
References: <333@stcvax.UUCP> <1332@sdcc7.UUCP> <729@sjuvax.UUCP>
Organization: [Consultant], Foster City, CA
Lines: 26

+---------------
| 	It is my understanding that no memory management hardware exists in the
| Mac as distributed, but it occurs to me that there may be a 68010 pin for
| pin replacement for the processor which might be made to do the trick....
| Jon Shapiro
+---------------

Sorry, a 68010 has no memory management in it, either. (For that matter,
neither does the 68020.) The '010 indeed IS a pin-for-pin replacement
for a 68000, but the ONLY difference as far as memory management goes
is that the '010 saves enough stuff on the stack when you get a "bus
error" trap (say, from a page fault) that you can re-start (actually,
continue) the affected instruction. The 68000 saves SOME stuff, but it's
not enough to always unambiguously continue.

All of the 680XX processors use an external MMU in order to do virtual
memory. (I actually prefer this, as sometimes you want to do it differently
than the way the chip maker provided.)

Rob Warnock
Systems Architecture Consultant

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