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From: adam@mit-amt.MEDIA.MIT.EDU (Adam Glass)
Newsgroups: comp.sys.mac,comp.sys.mac.programmer
Subject: Re: upgrading MacII to a 68030 machine
Message-ID: <653@mit-amt.MEDIA.MIT.EDU>
Date: 4 Sep 89 18:28:36 GMT
References: <763@swbatl.UUCP> <950@cbnewsk.ATT.COM>
Organization: MIT Media Lab, Cambridge, MA
Lines: 21

In article <950@cbnewsk.ATT.COM>, ech@cbnewsk.ATT.COM (ned.horvath) writes:
> You should also consider installing a PMMU ("real" MMU, 68581); Apple wants
> around $500 list (including installation), the great Harvey Mudd MUG dodge
> is costing me $170 plus installation.  Note that the '581 is a...

The PMMU (Paged Memory Management Unit) which allows "pages" of memory
to be swapped in and out of memory (and to/from disk) is the MC68851,
not the MC68581. Minor detail - or have I missed something, and there
really is a MC68581?

The MC68851 is a superset of the Apple MMU's functions. The MC68030 has the
MC68851 built in, and thus, '030 users do not need the PMMU to do A/UX and
virtual memory.

By the way, this is more of a comp.sys.mac.aux question, but does A/UX do
virtual memory? And is that the reason why you need an MC68851 chip to use
A/UX, or is there another reason.

Adam
--
(adam@media-lab.media.mit.edu) No .sig today. I'm bored and too tired to think.