Subject: PDP-8 in Space?

From: [email-masked] (Margaretha M. Guenther)
Date: 7 Mar 1994 01:16:01 GMT

Here's a dumb question:

Just how State-of-the-art is the PDP-8 ?   Are they in Space?

My husband gets a "Newsletter" from National Instruments in Austin, TX.

The Sring '94 edition has a drawing (I only look at the pictures) of an
experiment in the Space Shuttle Columbia in October '93 (p 11).

In this drawing there's a panel in the wall marked "PDP-8 Computer 
controlling experiment hardware and downlink."

I thought that the PDP-8 was an *old* and *heavy* computer with a Teletype
for input?

Was that a misprint, or is there really a PDP-8 in Space?

Meg. ________________?(^v^)?______________________________

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From: "Peter Weingartner" <[email-masked]>
Date: Tue, 8 Mar 1994 12:08:41 -0500

Well, I wasn't going to answer this (since I assumed there were people
out there who could answer the space bit [I can't]). Since no one has
replied, yet, here are my two cents:

In article <[email-masked]>,
>Just how State-of-the-art is the PDP-8 ?   Are they in Space?

I don't know about the PDP-8 being in space. I've never heard one way
or the other.

>I thought that the PDP-8 was an *old* and *heavy* computer with a Teletype

Well, the PDP-8 certainly is old, and the original computers certainly
would be on the heavy side. There are, however, more modern
implementations of the PDP-8 that are smaller and lighter. According
to the model FAQ, Intersil made a single chip implementation (the
6100) which was used in the VT78. Certainly, this could have been used
in space. Also, using TTL and modern PLD technology, you can implement
a PDP-8 on a ciruit board about a foot square (students here at IU do
that in our hardware sequence). I believe ('though I haven't had any
experience with this), that you could even implement a PDP-8 (without
memory) on a single FPGA. I do not know why you'd want to use a PDP-8
in space (perhaps because of its simple instruction set or its
time-tested quality :->), but there is no reason you couldn't find a small
enough implementation.

--pj

-- 
"As I understand it from eyewitness reports, the Scheme initiation ritual is 
 to sit in a circle around the Common Lisp manual and make gagging sounds and 
 jokes about how thick it is."  -- Scott E. Fahlman [email-masked]
 (It's true.)

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From: [email-masked] (Charles Lasner)
Date: 9 Mar 1994 00:45:03 GMT

In article <[email-masked]>,
Peter Weingartner <[email-masked]> wrote:

>memory) on a single FPGA.

The board of a DECmate III is 8" x 10" and that includes two VLSI chips
that talk to 10 interfaced devices.  The rest of the machine is just
metalwork, a power supply, a case, and a pair of floppy drives.  Stripped
down to a more appropriate minimal system, there is nothing particularly
deficient about a 6120-based PDP-8 system in terms of comparable
miniaturization to just about any other system.

The CPU doesn't really impact on this aspect of size.  Peripherals are
peripherals, and regardless of processor take up whatever space they need
to exist.

I once participated in a 6100-based project to produce a hand-held pdp-8
for a special application.  It was about the size and shape of a
calculator, and indeed, the only peripherals were a calc-type display and
minimal keypad.  Due to its low power consumption, the CMOS 6100 allowed
a smaller battery supply than some other designs.

Even the 1970-71 PDP-8/e is basically only a few square feet of boards.
The rest is the space to accomodate external memory and many
peripherals.  The actual single most problematic aspect with regard to
miniaturization is really the power supply!

So, the largest advance towards miniaturization often lies with the size
of the peripherals and power source, not what CPU is present!

cjl

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From: [email-masked] (Margaretha M. Guenther)
Date: 10 Mar 1994 14:12:20 GMT

> of the peripherals and power source, not what CPU is present!

Yes, a power supply is often the single largest component in a computer.
However, given an on-board DC supply to begin with, the largest part of
a power supply - the transformer - is eliminated. The next largest components,
the smoothing capacitors may also be absent.  What is left is a power dis-
tribution, rather than supply.

BTW,  I wrote the original posting about PDP8 in space, and the diagram
which I saw indicates a 19 inch rack mounted computer of about 8 inch height.

Anyone wanting a copy of the newsletter can call National Inst.
at 1-800-433-3488  and ask for "Instrumentation Newsletter" Vol 6, #1,
Spring 1994.  Tell them you heard of "Labview for Windows" and want to
see some articles on applications (PC data aquisition).

*DON'T* tell them who sent you.

Meg.

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From: [email-masked] (Douglas W. Jones,201H MLH,3193350740,3193382879)
Date: 10 Mar 1994 22:38:37 GMT

>From article <[email-masked]>,

> which I saw indicates a 19 inch rack mounted computer of about 8 inch

Sounds like the real thing.

					Doug Jones
					[email-masked]

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From: [email-masked] (Marc Ramsey)
Date: Tue, 15 Mar 1994 00:08:46 GMT

Margaretha M. Guenther ([email-masked]) wrote:
: In this drawing there's a panel in the wall marked "PDP-8 Computer 
: controlling experiment hardware and downlink."

: I thought that the PDP-8 was an *old* and *heavy* computer with a Teletype
: for input?

: Was that a misprint, or is there really a PDP-8 in Space?

In hopes of providing a pointer to more solid information, I remember
seeing years ago a photograph of the interior mockup of the ESA SpaceLab.
The most prominent feature of the mockup (to my eyes, anyway) was a PDP-8
front panel.  At the time, a PDP-8 was probably the logical choice for an
instrumentation computer, given the difficulties associated with changing
flight hardware, they may never have bothered upgrading the CPU.  Anyone 
have any recent pictures of the SpaceLab interior?