What's a PDP-24?

[Pat Barron]

In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".

I have no idea what a PDP-24 is ... DEC never produced anything with a
designation higher than PDP-16 (and even that wasn't even a "real"
computer, more a "roll your own machine out of RTM modules" kind of
thing). All I can think of is that maybe it was some kind of souped-up
PDP-12. Anyone know?

Link to the document I am referring to at
http://www.bitsavers.org/pdf/dec/pdp-x/03.pdf, if you want to look...

--Pat.

[Joe Pfeiffer]

Post by Pat Barron
In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".
I have no idea what a PDP-24 is ... DEC never produced anything with a
designation higher than PDP-16 (and even that wasn't even a "real"
computer, more a "roll your own machine out of RTM modules" kind of
thing). All I can think of is that maybe it was some kind of souped-up
PDP-12. Anyone know?
Link to the document I am referring to at
http://www.bitsavers.org/pdf/dec/pdp-x/03.pdf, if you want to look...

Interesting stuff.... seeing DeCastro's name on some of the memos,
could this be the machine that wound up as the DG Nova? I'd have to
read the rest of the memoes to see if it looked familiar...

[Tim Shoppa]

Post by Pat Barron
Link to the document I am referring to at
http://www.bitsavers.org/pdf/dec/pdp-x/03.pdf, if you want to look...

I can't help any with the PDP-24 reference, but in that memo deCastro
exactly maps out the evolution of minicomputer hardware
architecture/technology and realtime OS's for ten or fifteen years. Of
course he had a big hand at two of the biggest mini vendors of that
era, so whether he was prescient or simply steered everything that way
it's hard to say.

His "fourth generation design" desires for horizontal
system expansion were never quite realized
fully (although the part about the CPU taking over and replacing
peripheral processors is valid for the VAX-11/730 IDC, which
was like 15 years after his prediction.)

Tim..

[Lars Brinkhoff]

Post by Pat Barron
In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".
I have no idea what a PDP-24 is ... DEC never produced anything with a
designation higher than PDP-16 (and even that wasn't even a "real"
computer, more a "roll your own machine out of RTM modules" kind of
thing). All I can think of is that maybe it was some kind of souped-up
PDP-12. Anyone know?
Link to the document I am referring to at
http://www.bitsavers.org/pdf/dec/pdp-x/03.pdf, if you want to look...

Sorry (not really) for necroposting.

I also stumbled over this memo, and was also curious about this PDP-24.

Here are two places that mention PDP-24:
https://www.metafilter.com/100347/There-is-no-reason-for-any-individual-to-have-a-computer-in-his-home-RIP-Ken-Olsen-founder-of-Digital-Equipment-Corporation
http://vipclubmn.org/cpothers.html
I sent out some emails. The first really refers to a PDP-11/24.
The second should say DDP-24.

[Quadibloc]

Post by Pat Barron
In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".

I do remember reading that at one point, DEC was working on a design
for the PDP-3 which would have had a 24-bit word.

John Savard

[Quadibloc]

Post by Quadibloc

Post by Pat Barron
In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".

I do remember reading that at one point, DEC was working on a design
for the PDP-3 which would have had a 24-bit word.

I see I'm mistaken. It was the PDP-2 which would have had a 24-bit word;
the PDP-3 was a one-off for the CIA which was a 36-bit version of the
PDP-1.

John Savard

[Lars Brinkhoff]

Post by Quadibloc

Post by Quadibloc

Post by Pat Barron
In looking through some old DEC memos on bitsavers.org concerning
"PDP-X" (a proposed, but never built, DEC computer), I saw an
interesting tidbit about how this machine was intended to "replace the
present PDP-8, PDP-9, and PDP-24".

I do remember reading that at one point, DEC was working on a design
for the PDP-3 which would have had a 24-bit word.

I see I'm mistaken. It was the PDP-2 which would have had a 24-bit word;
the PDP-3 was a one-off for the CIA which was a 36-bit version of the
PDP-1.

Yes, so the lore goes. But according to some rumors, the 24-bit PDP-2
was never built (but see below!). And the timeframe seems off for de
Castro to mention it alongside the PDP-8 and PDP-9.

As long as we're feeding the rumor mill, there was this one mention of
a so called "PDP-2 ½" in an alt.sys.pdp10 message by Max ben-Aaron
dated February 1997:

"In the late 60's & early 70's I worked for a company (Medidata, later
Searle Medidata) which started life as a not-for-profit spin-off from
Lincoln Lab (as I have heard), called American Science Institute.
The chief engineer, Ed Rawson was a friend of DEC's Olsen and he
managed to get hold of the modules used for the prototype PDP-2
which never reached the market. ASI used them to build their own
machine (designed, I believe, by Chuck Corderman) which they called
"Casino" and was sometimes jocularly referred to as a PDP-2 1/2.
Casino was noteworthy for having, very early in the game, graphics
capabilities. It also had some special terminals which had labels
that cannot be repeated on this (family) newsgroup."

[Quadibloc]

Yes, so the lore goes. But according to some rumors, the 24-bit PDP-2
was never built (but see below!).

Supposedly, it was never even designed. So the ASI Casino will be
very interesting to hear about...

John Savard

[Lars Brinkhoff]

Post by Quadibloc

Yes, so the lore goes. But according to some rumors, the 24-bit PDP-2
was never built (but see below!).

Supposedly, it was never even designed. So the ASI Casino will be
very interesting to hear about...

Interesting indeed, but hard to find any information.

On page 5 here is a letter from Edward B. Rawson, then at Searle Medidata:
http://tcm.computerhistory.org/CHMfiles/Memos%20Regarding%20Start%20of%20DEC%20Musuem%201972-1975.pdf

[Rich Alderson]

Post by Lars Brinkhoff

Post by Quadibloc

Yes, so the lore goes. But according to some rumors, the 24-bit PDP-2
was never built (but see below!).

Supposedly, it was never even designed. So the ASI Casino will be
very interesting to hear about...

Interesting indeed, but hard to find any information.
http://tcm.computerhistory.org/CHMfiles/Memos%20Regarding%20Start%20of%20DEC%20Musuem%201972-1975.pdf

According to a footnote in the chapter on early DEC history in Bell's _Computer
Engineering_ both the PDP-2 and the PDP-3 were "paper designs". It goes on to
state that no PDP-2 was ever built but that a customer (not the CIA, BTW) built
a PDP-3 from said design. It was apparently a word-extended PDP-1, unrelated
to the later 36 bit design of the PDP-6/PDP-10.

[Quadibloc]

Post by Lars Brinkhoff
"In the late 60's & early 70's I worked for a company (Medidata, later
Searle Medidata) which started life as a not-for-profit spin-off from
Lincoln Lab (as I have heard), called American Science Institute.
The chief engineer, Ed Rawson was a friend of DEC's Olsen and he
managed to get hold of the modules used for the prototype PDP-2
which never reached the market. ASI used them to build their own
machine (designed, I believe, by Chuck Corderman) which they called
"Casino" and was sometimes jocularly referred to as a PDP-2 1/2.
Casino was noteworthy for having, very early in the game, graphics
capabilities. It also had some special terminals which had labels
that cannot be repeated on this (family) newsgroup."

I am aware of a company called ASI that made some computers with
unusual word lengths, among them the ASI 210 with a 21-bit word.

But they also made the ASI 6020, which does have a 24-bit word.

John Savard

[Lars Brinkhoff]

Post by Quadibloc

Post by Lars Brinkhoff
"In the late 60's & early 70's I worked for a company (Medidata, later
Searle Medidata) which started life as a not-for-profit spin-off from
Lincoln Lab (as I have heard), called American Science Institute.
The chief engineer, Ed Rawson was a friend of DEC's Olsen and he
managed to get hold of the modules used for the prototype PDP-2
which never reached the market. ASI used them to build their own
machine (designed, I believe, by Chuck Corderman) which they called
"Casino" and was sometimes jocularly referred to as a PDP-2 1/2.
Casino was noteworthy for having, very early in the game, graphics
capabilities. It also had some special terminals which had labels
that cannot be repeated on this (family) newsgroup."

I am aware of a company called ASI that made some computers with
unusual word lengths, among them the ASI 210 with a 21-bit word.
But they also made the ASI 6020, which does have a 24-bit word.

It seems Casino is the right name. From the TCM letter:

"As you may have heard, we have been considering the question of
what to do with our CASINO computer. The machine is nearing the end of
its useful life. We have recently purchased a General Radio 1792 to supply
the board testing function now being carried out on CASINO. I anticipate
that within six to nine months we will have no further use for CASINO."

[Quadibloc]

Post by Lars Brinkhoff
"In the late 60's & early 70's I worked for a company (Medidata, later
Searle Medidata) which started life as a not-for-profit spin-off from
Lincoln Lab (as I have heard), called American Science Institute.

Okay, the ASI I'm thinking of, that made the ASI 6024, was Advanced
Scientific Instruments.

John Savard