12 Apr
2007
12 Apr
'07
6:29 a.m.
Michael A. Ryan wrote:
I have added a few new pictures to the xt/370 web site
showing the stacked (and non-stacked) versions of the MCM66128L20, as well as two other
examples of IBM engineering that employed stacked chips (AT motherboard and PC memory
card) in the early 1980's.
There are 36 pairs on the AT board to get 512K and 18 pairs on the memory card to get
64K.
Obviously, these chips have different pinouts (at least select).
The url is:- www.xt370.net click on the link to the left, 'Memory Technology'
The question a data sheet might answer is:- does one of the new MCM66128L20 parts
replace one of the old stacked pairs?
Mike, your web page says:
"The System/370 processor is implemented in three microprocessors --
two Motorola 68000 processors and a custom 8087."
Are you sure about that? Nick Tredennick, the architect (or maybe co
architect) of the 68000 left Motorola, went to work for IBM, and was the
architect of the "micro 370". The design and its evolution were
described in a book Tredennick wrote, Microprocessor Logic Design: The
Flowchart Method.
I know nothing of the machine you have there, but I suspect it is really
using redundant copies of the micro 370 described in the book. I've
heard passing reference to this machine and have heard that it is a
68000 CPU with modified microcode, but that isn't the case. They have
similarities at some level because of the era they were design and
because of Tredennick's contribution to both.
Perhaps you are write and there was more than one micro 370 project, but
I thought I'd mention the piece of the puzzle that I know a little about.