non-binary computers?

From: David C. Jenner <>
Date: Thu Sep 2 19:24:22 1999

The IBM 360 series was a "hexadecimal" machine. The result was that
you got one or more fewer decimal digits of precision for floating
point numbers as opposed to a binary machine. The CDC series of
3xxx/6xxx was a favorite of scientifically oriented users due to
this fact, and many computer centers were CDC instead of IBM at the
time. (There was a difference in word length, too, but many users
didn't realize that you could get better precision on a PDP-11
than on a 360 in single precision.)

The ultimate, of course, is the UNARY computer. If you look in the
"Feynman Lectures on Computation", Richard Feynman, 1996, you'll see
that he has you start designing a unary computer. Maybe not so easy
when all you have to work with is "1"! (It has to have a variable
word length, of course).


Mark Green wrote:
> > I recall reading an article a while back about the possibility of
> > building computers based on a number system other than two (octal, IIRC).
> > If memory serves me right, it was found possible to do, but not
> > practical and less efficient than binary.
> >
> > I now have need for some basic information on the possibility of
> > non-binary computers, but am unable to find anything. Can anybody point
> > me in the direction of some info?
> >
> A number of early small computers were non-binary. One that comes
> to mind is the IBM 1620 which was a decimal variable word lenght
> machine. The 1620 was in production about 40 years ago and was
> mainly marketed as a business machine. One of the interesting
> features of this machine was that it did all its arthmetic by
> table lookup. The tables were stored in memory, so you could change
> how the operations worked! A number of 1620s were used by universities
> into the late 1960s. Since they were variable word length, they
> were very nice for doing precise computations.
> Since early computers were based on analogue electronics it was
> much easier to do non-binary than it is now. Many early memory
> devices (except core) were really analogue devices with thresholds
> used to distinguish 0 and 1. You just needed to add a few more
> thresholds to get a larger range.
> --
> Dr. Mark Green
> Professor (780) 492-4584
> Director, Research Institute for Multimedia Systems (RIMS)
> Department of Computing Science (780) 492-1071 (FAX)
> University of Alberta, Edmonton, Alberta, T6G 2H1, Canada
Received on Thu Sep 02 1999 - 19:24:22 BST

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