This page contains miscellaneous information about the IBM 1620 which either
doesn't fit in any other section of this web site or bears repeating.
Here, in no particular order, are some interesting facts:
Within IBM, the original development code name for the IBM 1620 was CADET. It
was later that someone made up the acronym for CADET - Can't Add,
Doesn't Even Try. This reflected the fact that the 1620
had arithmetic tables in memory which must be loaded with a program for it to
be able to perform arithmetic operations.
The 1969 Universal Pictures' movie - Colossus: The Forbin Project - used
about a dozen IBM 1620 control panels as part of the super computer Colossus.
On the IBM 1620 Model 1, one could rewrite the arithmetic tables to force the
machine to do arithmetic in any number base less than or equal to 10.
Memory was so tight on the IBM 1620, that SPS (assembly) programmers resorted to
every trick imaginable including dynamic modification of instruction op codes
and/or addresses, burying small data items inside instructions, overwriting
early instructions with later data, etc. In short, everything that is forbidden
by modern software practices.
The first Fortran translator on the IBM 1620 didn't include the FORMAT
The core memory on the IBM 1620 was heated to 104 degrees Fahrenheit to stablize
it's operating characteristics. It was easier and cheaper to maintain the
temperature if the core were heated than if it were cooled.
The console typewriter carriage on the IBM 1620 Model 1 extended beyond the
table top. The carriage return operation was so forceful that one could be
hurt if standing too close. So a wire metal "ball guard" was added to the
typewriter to keep people from standing in the danger zone.
It is easy to tell the difference between the IBM 1620 Models 1 and 2 by their
console typewriter. All Model 1's used an IBM Executive Model B typewriter
while all Model 2's had an IBM Selectric typewriter.
Ray Kurzweil (Kurzweil Technologies) developed the first computerized four-way
analysis of variance statistical package. It was written for the IBM 1620. The
program could handle up to four-way analyses, missing data and unequal subset
After the IBM 1620 Model 2 was developed there were plans to build a "turbo"
version of it code named '1620-V8'. Many engineers were assigned to the project
but then it was cancelled ("redirected").
When the IBM 1620 was first announced, Datamation magazine commented that
it was the first IBM computer system which had a monthly rental price less than
the machine's model number.
The first production version of the well-known civil engineering software
package - COGO - was implemented on the IBM 1620 at the Puerto Rico Bureau of
Highways. It was written in a combination of Fortran and machine code by
Charles L. Miller in "a relatively few days".
In the article Changes in Computer Performance in the September
1966 issue of Datamation magazine, Dr. Kenneth E. Knight assigned
sequential "serial" numbers to almost all digital computers known. He assigned
number 125 to the IBM 1620 Model 1 and the number 213 to the IBM 1620 Model 2.
According to the Utah State University Applied Statistics department, they
received the first IBM 1620 delivered west of the Mississippi.
IBM produced a total of 1300 IBM 1620 Model 1 and 2 computers in the United
States and 660 systems internationally. More Model 2 computers were built than
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