2. What Mike Alexander remembers

posted Sep 13, 2010, 8:14 AM by Jeff Ogden   [ updated Mar 11, 2014, 6:09 AM ]
From: Mike Alexander
Date: June 22, 2010 1:31:13 AM EDT
To: Jeff Ogden, Scott Gerstenberger
Cc: Bruce Arden
Subject: Re: Blaauw Box and the 360/67

This [the description of the Blaauw Box in Wikipedia, see note #1 below] is almost completely wrong.  Bruce clearly knows a lot more about this than I do, since he was a major player in it and this all happened just as I joined the Computing Center in 1965, and I've CCed him so he can correct my mistakes.  However here's what I think happened.

There were several universities and research centers (UM, MIT, GM Research, NASA Lewis (?), and others?) who were interested in getting a machine for time sharing.  They proposed an address translation system along the lines described in the paper "Program and Addressing Structure in a Time-Sharing Environment" by Arden, Galler, O'Brien, and Westervelt.  This described a two level address translation architecture much like what is still used today.  IBM didn't go for this idea and instead proposed the Blaauw Box which implemented a single level address translation.  They totally missed the idea of using the two level translation to control sharing of memory among processes.

IBM went back and forth with the consortium and things were getting nowhere.  On the other hand GE was happy to implement something like what the consortium wanted.  Eventually MIT gave up and ordered a GE machine (which is why Multics was written for GE architecture instead of IBM).  UM was very close to following their lead.  At that time the university/research market was still important to IBM and they were so worried about losing it all to GE that they agreed to implement the architecture the consortium wanted.  The result was the 360/66M (or maybe /65M), a special order machine for the remaining members of the consortium.  After IBM discovered that there was wider demand for this machine, they renumbered it as the 360/67 and made it part of the product line.

The DAT box on the 360/67 did not implement the Blaauw box.  It implemented the architecture described in the paper mentioned above.

Someone should fix the Wikipedia article, .... [I did that, -Jeff] I imagine there are documents in the Bentley that cover this period in the Computing Center history.

      Mike

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