2 Sep
1999
2 Sep
'99
12:24 p.m.
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).
Dave
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 mark(a)cs.ualberta.ca
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