[part 1 of 2 parts]
Post by gah
I have both "Memories that Shaped and Industry" and
"IBM's 360 and Early 370 Systems", are those the ones
that get it wrong?
I have only the latter, but I have not read it in years. What
I do remember is that virtually everywhere I go on the web,
and in most books I have actually read, they get the very fine
details (mostly, the time sequence) of what actually happened
wrong. I'd have to check my copies to answer your question.
But it's really not that important, obviously. I just hate it
when folks mindlessly pick up something they read online, and
accept it as authoritative because it sounds that way. If I
were writing a book for a reputable publisher, their fact
checkers would have a tiff with me because most places they
could go to check facts (that I have found) just have them
plain wrong to begin with. So, I'd probably get "corrected."
At least what I know is now being archived, here if nowhere
For example, look at this web site:
Unless the first part was talking about a specific machine that
was installed at some specific customer site, this page is very
confused about the maximum amount of memory that a Model 91 can
have. It first says it's 4 MB, and then just below it says 6 MB.
The first two sources they mention are books that I have, but I
have not yet checked them for accuracy. But I bet they get some
of the details wrong. The guys that wrote those books were not
working at this level of detail on a daily basis (if ever), so
I would not even expect them to recognize mistakes of this sort.
Quite understandable, in fact. But the publisher's fact checkers
should have made them prove it, since these books were actually
little more than collections of facts (not much plot, anyway).
Obviously, they didn't do that. Go figure.
Even this IBM web site:
indicates that a 360/95 can have from 1 MB to 6 MB of 780 ns
storage. Along with the 1 MB of thin-film storage every Model
95 had (yeah, all two of them!) that would add up to a max of
7 MB, not 5 MB as most sources indicate. More on that issue,
later (below). At this point (40 years later, almost exactly)
it is probably like counting angels on the head of a pin, and
who knows what actual differences there were between the ten
or twenty (more on THAT later, too) Model 91s and the two 95s.
The two 95s, for example, could actually have had provision
for attaching 6 MB of additional core storage, but that would
have required a third "Storage Control Element." A Model 91
had two storage control elements, one for the left side of
the box, and one for the right. The "Main Storage Control
Element" was connected to the "High Performance Main Storage"
(HPMS) unit, which was (more on this, later) a 2395 Model 1.
The "Peripheral Storage Control Element" was connected to the
"Extended Main Storage" (EMS) unit, which was either a 2395
Model 1 or 2. Now, I VERY STRONGLY SUSPECT that in the only
two real Model 95 that IBM built the thin-film monolithic
memory was attached to the Main Storage Control Element. The
fact that Models 91 and 95 had two distinct Storage Control
Elements in the first place was due to the fact that what
became the 95 had to support BOTH the 1 MB thin-film stuff
as well as ordinary core memory. Thus, although no Functional
Characteristics manuals exist for the Model 95, I'll bet just
about anyone that the Main Storage Control Element, which had
higher performance than the Peripheral Storage Control Element
in the first place, was the attachment point for, and was
exclusively dedicated to, the thin-film memory. This left the
slower Peripheral Storage Control Element available for the
4 MB 2395-2 core storage "H box." All of this, therefore, just
means that, for obvious technical reasons, the maximum storage
capacity of any Model 95 (as then designed) was 1 MB + 4 MB =
5 MB, not 7 MB. (If it had been anything else, it would not
have been a 95, but a 91.) So, I don't have to know very much
about two machines that were special order-built to be able
to know this fact. All I have to know is that the 95 was a 91
and how all 91s were constructed internally. But what I still
do not know is if the two 95s had one 2 MB 2395-1 core storage
unit or one 4 MB 2395-2 core storage unit actually installed.
I believe that I remember being told that one had 3 MB total,
and another had 5 MB total. If so, one came with a 2395-1 and
the other came with a 2395-2. But all my contacts at NASA in
NYC are long lost, so I doubt that we will ever actually know.
Here is another IBM web page:
"The Model 95 -- two of which were installed in 1968 at NASA's
Goddard Space Flight Center in Greenbelt, Md. -- were used to
solve space exploration problems requiring unusually high
But then here is another site:
"Only two IBM 360/95 computers were made, both for NASA. One
went to the Goddard Space Flight Center, in Greenbelt, [MD],
and the other went to the Goddard Institute for Space Studies,
part of Columbia University, in New York City."
Guess which one is right? Not the first (IBM) one! But how do
I know? Well, let's take a look at another IBM web site:
Here we can read:
"One model of the System/360, the 95, was built
especially for NASA, and only two units were made.
One went to Goddard Space Flight Center in
Maryland; the other to the Goddard Institute for
Space Studies on upper Broadway in Manhattan.
David B. Soll, who is currently a senior technical staff
member for IBM's Business Continuity and Recovery
Services, was a NASA contractor at GISS in New
York in the 1970s and 1980s. "The model 95 was a
supercomputer of its day," he said recently. "With it,
we carried out research in Meteorology and
Climatology, developed instrumentation for a Landsat
satellite to measure agricultural data, and instruments
that traveled to Venus and Jupiter aboard the
Pioneer Venus and Galileo spacecraft." "
Now that sounds a little more authoritative. But if you look
at the picture on page 38 of that document, you will see that
it is identical to one on many other web pages that Google
will easily reveal to you where it is described as a 360/91!
Here are the most egregious two examples:
My question now is: Is that picture of a Model 91 or of
a Model 95? And where was it taken, exactly? Who are the
people? (I bet they are IBM, or IBM contractors, not NASA
But then this web page:
seems to say (and we don't even have to read too much between
the lines) that both Model 95 went to Greenbelt, MD:
"Formal acceptance of two, new super-speed computers -- IBM
System/360 Model 95s -- by NASA's Goddard Space Flight Center
was announced here (Washington, D.C.) today by International
Business Machines Corporation.
"The two computers are the first and only ones in IBM's Model
90 series equipped with ultra-high-speed thin-film memories.
Over a million characters (bytes) of information are stored
in each on magnetic "spots" four millionths of an inch thick.
"Both of NASA's Model 95s are handling space exploration problems
which require unusually high computation speeds.
"One Model 95 is the primary data processing facility for the
Center's Tracking and Data Systems Directorate. It provides
additional computing support to the Project, Technology and
Systems Reliability Directorates.
"The second Model 95 is being used by astrophysicists at NASA
to create massive mathematical models of the universe. The
boost in computing capability is enabling them to simulate
the evolution of galaxies, stars and planets to a degree
never before possible."
But they really didn't say exactly where the second one went,
now did they? I happened to know a programmer who worked at
NASA at Columbia University. He told me about the Model 95
they had there long before this most recent IBM document was
researched and appeared. He was in a position to know. And I
trust him. But that still does not answer the question about
which machine is actually in which picture. I may never know
and nobody will unless one of the original participants ever
shows up (or the photographer). The 95 and the 91 console
were identical, so we can't tell them apart even if we did
have a good sharp photograph to analyze (which we don't).
NASA had one 360/95 at NASA (per se), but they also had some
360/91s, one of them being particularly famous, and that may
have confused the poor (young) folks at IBM who researched
and prepared material both for ex-IBM executives who wanted
to write books as well as present-day IBM history web sites.
Others are confused about the shipping dates and sequence of
Models 91 and 95, not just their basic, raw specifications.
Many disagree on the number of 360/91s that IBM built or sold.
I have read and heard it authoritatively stated that the number
was 10, 11, 12, 14, 15, or 20. The above web site states:
"According to IBM's 360 and Early 370 Systems by Pugh, Johnson,
and Palmer, IBM produced fourteen Model 91 computers, four of
which it kept for internal use."
Oh, my! What should we believe? I think, but cannot prove, that
the actual number was 15, and IBM may indeed have kept four of
them. That would be consistent with other reports that IBM SOLD
11 360/91s. That figure (the number actually SOLD) would figure
(pun intended) later in IBM's legal briar patch over the CDC 6600
reaction issue. So, while I cannot PROVE that IBM built 15, I
have a pretty good idea that's the truth, and many other facts
are consistent with that figure. Still, most web sites (and, I
suspect, most books) get the number wrong. Again, not important
except that if the point of some document is to get facts right,
shouldn't they be right or at least advertised as "reported" or
[continued in part 2]