PDP-1 and PDP-4 architecture????

From: Roger Ivie <IVIE_at_cc.usu.edu>
Date: Fri Mar 24 16:53:22 2000

>I am looking here for info about the differences between the PDP-1 and PDP-4
>architecture.

Bell & Newell's out of print book about computer architecture runs through
both architectures (as well as many others). Unfortunately, I don't have a
copy so I can't be more specific. I can't even find the photocopies I made
of this and other information (I have a couple of large three-ring binders
chock full o' architecture descriptions ranging from EDSAC to modern stuff;
but my office has moved a couple of times since then, so I've misplaced
them).

> Can PDP-1 software run on a PDP-4?

No. The PDP-4 was designed to be able to use PDP-1 memory and I/O devices
(IIRC), but the instruction set is different. The instruction set of the
PDP-4 is essentially that used by the PDP-7, PDP-9, and PDP-15; the
Bell&Newell book (IIR the source C) claimed the primary difference between
the PDP-4 and the PDP-7 was that the PDP-7 used ASCII I/O devices while the
PDP-4 used a six bit code.

The true mystery is, of course, the PDP-3. It was allegedly a 36-bit
version of the PDP-1. I've seen one source that had a drawing of the word
format for the PDP-3, but no other information (the source was an "encyclopedia
of computers" circa 1960 that was composed of two-page descriptions of each
machine which appeared to be taken from the marketing literature for the
machine. The PDP-3 was listed, a word format was given, and a couple of
trivial benchmarkish statistics; time to perform an add, IIRC. I have a copy
of the blurb in the aforementioned three-ring binders which I can't find).
Rumor has it that a DEC customer built a PDP-3, but DEC never did.

Roger Ivie
ivie_at_cc.usu.edu
Received on Fri Mar 24 2000 - 16:53:22 GMT