[ih] A small story of IMP #1 and the UCLA Computer Club

Mon Jun 1 16:28:45 PDT 2026

We once convinced a poor undergrad that every night, the operator had to empty the bit-bucket from all of the left and right shifts during the day. To convince the poor student, they were shown the card chad from a keypunch no one used.

> On Jun 1, 2026, at 17:37, Vint Cerf via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> While we are in anecdote mode, the Sigma-7, like other processors, could be
> used to toggle a flip-flop at various rates to produce sound. This was
> usually accomplished by putting the machine into a loop with a certain
> repetition rate. One of the senior graduate students was into computer
> music. One day, I brought a friend to see the Sigma-7 and the IMP. When we
> arrived, the sr. grad. had a set of tuning forks and was adjusting the loop
> lengths to match the sounds of the tuning forks. As we approached, I
> cautioned my guest to be quiet. "He's tuning the computer, I said...."
> 
> v
> 
> 
> On Mon, Jun 1, 2026 at 5:21 PM Andrew G. Malis via Internet-history <
> internet-history at elists.isoc.org> wrote:
> 
>> Craig,
>> 
>> I did my share of Pluribus coding and debugging. The assembly code was
>> really no worse than any other once you got the hang of it, it was actually
>> somewhat similar to PDP-11 assembler. It was a multiprocessor machine, and
>> if any of the processors crashed, the remaining processors would notice,
>> send a fresh code reload to the failed processor, and restart it. As a
>> result, it was a pain to try to debug issues in the field, although crashes
>> would produce dumps for later analysis. The easiest way to debug the code
>> in the lab was to shut down all but one processor. We were able to shut
>> down (and keep down) individual processors by using the front panel
>> switches to write "FADE" into a particular location. We could later reboot
>> the FADEd processor(s) manually.
>> 
>> Regarding physically stopping a Pluribus by bullets or hand grenade, I
>> certainly believe a hand grenade would damage all of the processors enough
>> to bring them all down. One well-placed bullet in each processor would
>> probably do it as well, but you would have to do it carefully, not just
>> fire willy-nilly at the collection of processors, you could easily miss at
>> least one of the processors that way.
>> 
>> Cheers,
>> Andy
>> 
>> 
>> 
>> On Mon, Jun 1, 2026 at 3:40 PM Craig Partridge via Internet-history <
>> internet-history at elists.isoc.org> wrote:
>> 
>>> By the time I joined BBN, the story was that the person shooting the
>>> Pluribus had been forced to write programs for it.  It had a BBN-wide
>>> reputation for not being programmer-friendly (which is saying something,
>> as
>>> BBN periodically generated computing platforms which were painful to
>>> program -- such as the C70 with 10-bit bytes).
>>> 
>>> Craig
>>> 
>>> On Mon, Jun 1, 2026 at 12:41 PM Jack Haverty via Internet-history <
>>> internet-history at elists.isoc.org> wrote:
>>> 
>>>> Another IMP story...
>>>> 
>>>> The "Pluribus" computer was a BBN creation that included highly
>>>> redundant hardware, with multiple everythings.   The idea was that no
>>>> matter what failed, the system would keep running while repairs were
>>>> made.  Of course a Pluribus could be used as an IMP, which was popular
>>>> in some government installations.  One day at BBN, I heard this story.
>>>> Wasn't there myself, but I can believe it.
>>>> 
>>>> A Pluribus IMP was being decommissioned at some government site.  They
>>>> happened to have a variety of military stuff around.   So someone
>>>> decided to see if the Pluribus IMP was as reliable as it was touted to
>>> be.
>>>> 
>>>> The IMP was set up, still running.   Someone got a rifle (M-16?) and
>>>> started shooting at the IMP.  Really.  Sadly I don't recall the number,
>>>> but the IMP survived an amazing number of direct hits at point blank
>>>> range, and still kept passing traffic.
>>>> 
>>>> Where did those folks in the Computer Club go after leaving UCLA...?
>>>> Any of them in ROTC?
>>>> 
>>>> /Jack
>>>> 
>>>> On 6/1/26 11:22, Karl Auerbach via Internet-history wrote:
>>>>> This is a trivial, and quite irreverent, bit of Internet history....
>>>>> 
>>>>> I, like several others, were members of the UCLA computer club during
>>>>> the late 1960's.  The club's office was in Boelter Hall - not far
>> from
>>>>> the room that held IMP #1 (and the Sigma computer - along with its
>>>>> "Sigma EXecutive" documentation, aka "SEX Manuals".  My project's
>>>>> computer, an IBM 7094 - with a true memory leak [the core memory was
>>>>> oil cooled, and that oil leaked] - was in the next room over and we
>>>>> could hear the squeals from the AM radio caused by the RF noise from
>>>>> the IMP and the Sigma.)
>>>>> 
>>>>> Anyway, folks in the Computer Club - especially Mark Kampe - kinda
>>>>> like to pull pranks.  For instance, we would drop things from the top
>>>>> of Boelter Hall (9 floors up) to see what would happen.  The landing
>>>>> zone was the collection of crunched and bent automobiles resulting
>>>>> from the early crash-tests of my group, the Institute of Traffic and
>>>>> Traffic Engineering.  We dropped everything from frozen superballs to
>>>>> a lead container used to hold/transport radioactive materials [it was
>>>>> empty].  There was also a feisty ice-cream vending machine in the
>>>>> hallway that once-too-often failed to deliver the paid-for frozen
>>>>> treat - so someone in the club unplugged the machine for a few hours,
>>>>> everything inside melted, and then plugged it back in, re-frezzing
>> the
>>>>> leaking drippy mess.  That was not nice, but it was - here's a
>>>>> terrible pun - that vending machine received its just desserts.
>>>>> 
>>>>> Anyway, back to Internet History...
>>>>> 
>>>>> IMP #1 had the rough appearance of an armor plated refrigerator, with
>>>>> lifting lugs on the top.  The machine was "ruggedized".
>>>>> 
>>>>> That word, ruggedized, was like honey to ants - it seriously caught
>>>>> our attention.  So we (I think Mark K. in particular) asked "Is it
>>>>> rugged enough to survive a drop from the top of Boelter Hall?".
>>>>> 
>>>>> So our imaginations lit up with images of us grabbing IMP #1, hauling
>>>>> it up to the roof and dropping it into the crashed cars nine floors
>>>>> below.
>>>>> 
>>>>> Obviously, prudence and sanity - and perhaps even some, probably
>>>>> reluctant, respect for law - prevailed.  We never did get beyond the
>>>>> "what if we did this" stage.
>>>>> 
>>>>> (But a couple of years later some of us migrated from UCLA to SDC in
>>>>> Santa Monica.  At SDC we had an extremely awful HP 2000 minicomputer
>>>>> that, if I remember properly, did actually suffer such a fate as it
>>>>> was dropped it from the roof of the Q7A building - three stories tall
>>>>> - onto the parking lot - a fate that all of us applauded. [It was
>>>>> truly a terrible machine with an even worse operating system.]  Some
>>>>> of use, years later, moved onto the Interop show nets were we
>> sometime
>>>>> had to practice the delicate art of percussive maintenance.)
>>>>> 
>>>>>        --karl--
>>>>> 
>>>> 
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