Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!agate!violet.berkeley.edu!steve
From: steve@violet.berkeley.edu (Steve Goldfield)
Newsgroups: comp.sys.mac
Subject: Re: PMMU
Keywords: How to install
Message-ID: <1989Sep1.204210.7417@agate.uucp>
Date: 1 Sep 89 20:42:10 GMT
References: <15454@duke.cs.duke.edu>
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In article <15454@duke.cs.duke.edu> aff@lear.cs.duke.edu (Amr F. Fahmy) writes:
#>I got the 68851 and the 68882 for my mac II. Can somebody please tell me
#>how to install and test them. Thanks.
#>
#>Amr F. Fahmy
#>aff@duke.edu

Somebody sent me a file of instructions I can't find. But
here's what I remember. You will have to disassemble your
Mac II by taking off the cover and removing the panel with
the two disk drives (assuming you have a hard disk). Just
a matter of removing the screws and unplugging a few cables.
If you haven't done so before, note that the cables have a
stripe on one end. Make a rough diagram of where the stripes
are to make sure you reconnect them properly. At this point,
you need some kind of grounding cable. What I did was to get
a couple of feet of copper wire and hook one end to the chassis
and wrap the other around the wrist with which I picked up the
chip. It is important that there not be a voltage difference
between the chip and the Mac II if you don't want to destroy
the chip. [[Note that you turned the Mac II off and even
unplugged it to be doubly safe before doing any of the above.]]
Now you can carefully remove your 68881 and the cap over the
68851. Again note that one corner of the chip has a metal V
and that the board has a corresponding mark. The new chips
should be oriented in the same way. It takes a fair amount of
pressure to remove and insert these chips. I used a thin
screwdriver to pry around the edges of the 68881 and the
plastic cap. Be careful not to put too much pressure on
the printed-circuit board. The person who sent my instructions
recommended placing something flat under the board, but I
managed to get my chips in and out by using only moderate
pressure.

Once the chips are down (sorry about the pun), reassemble
your Mac II. Start up your Mac II. One view holds that if
it still works, you inserted the chips correctly.
If you download Macenvy from sumex, it will tell you what
hardware and software are in your system. It will note the
presence of the PMMU. The current version will say you have
a 68881 rather than a 68882 because it only checks to see
that the chip is there. There is also a patch for Excel,
which also says it sees a 68881. I have the patch, but I
don't know enough to know how to install it or to tell
anyone else how. (If anyone can tell me what software to
use to do so, I'd appreciate the information. In other words,
in CP/M, I'd use ddt. What's the Mac equivalent?)

Frankly, I haven't found much software which takes advantage of
the 68882. And the PMMU won't do you any good unless you have
the available software which facilitates virtual memory. But
at least you'll have the satisfaction of knowing you can use
System 7.0 fully as soon as it arrives, assuming it lives up
to preliminary expectations.

Excel patch follows: (I assume that Ken Hancock won't object
to my posting the mail he kindly sent me)

To make Excel version 1.5 recognize the 68882 Math Coprocessor 
(which comes on the SE/30, Mac IIx, and Mac IIcx) instead of the 
68881 which comes on the Mac II), make the following modifications:

search for:   6620 4A42 675C
replace with: 6D20 4A42 675C

The logon will still say that the 68881 coprocessor is installed,
but it will use the 68882 instead.

-- 
Ken Hancock  '90                    | E-mail: (BITNET/UUCP/INTERNET)
Computer Resource Center Consultant |   isle@eleazar.dartmouth.edu
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