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From: rosen@cs.utexas.edu (Eric Carl Rosen)
Newsgroups: comp.sys.mac.hardware
Subject: Re: PMMU on MAC II
Summary: Easy to install
Keywords: 68551 PMMU68551 PMMU68551 PMMU68551 PMMU68551 PMMU68551 PMMU
Message-ID: <1180@yoakum.cs.utexas.edu>
Date: 14 Mar 91 01:25:49 GMT
References: <1991Mar14.000400.9025@mcs.drexel.edu>
Organization: Dept of Computer Sciences, UTexas, Austin
Lines: 17

[Yuram N. Yifrah] writes:
>Could someone plase help me with a question. What is involved in replacing
>the HMMU with the 68551 PMMU in a plain Mac II? And can it be reversed.   

As far as I know, you merely need to locate the appropriate chip (NOT the
one marked 68020 and NOT the one marked 68881 :) ), remove it carefully (a
flat blade screwdriver might be helpful here if you don't have a chip extractor
kit), and replace it with the 68551. Make sure to insert it in the proper
orientation, but I believe the pins will only line up one way. In any event,
no soldering is involved. As far as I know, this is all you need to do. I did
this and System 6.0.5 recognizes the chip.

Of course, I won't be responsible if you follow the above directions and
destroy your machine, or even if the directions above are incorrect. However,
from personal experience, I honestly believe this is all you need to do.

--Eric