[ih] The IMP Lights story (Was: Nit-picking an origin story)

[Bob Purvy]

Oddly enough, I just made a transcript of my podcast interview with Dick
Sonderegger, who knew the *The Soul of a New Machine* guys at Data General.
He reviewed their Programmer's Reference doc for the Nova, and it said,
"when the light goes out, the computer stops."

Technically true.

By the way, everyone: text transcription has made huge leaps forward
lately. You can get software for your own machine (MacWhisper is what I
used) that's free, and does a WAY better job than even 5 years ago. If
you've got some old voice recordings of IETF meetings, give it a shot. Mine
only needed some light editing to be usable.

On Sun, Aug 24, 2025 at 11:26 AM Steve Crocker via Internet-history <
internet-history at elists.isoc.org> wrote:

> Folks,
>
> On Monday, 18 August 2025, I described how the lights on the IMPs often
> burned out and caused a noticeable amount of downtime on the IMPs.  Geoff
> Goodfellow asked for more details.  That exchange is copied below.
>
> I learned of the problem with the IMP lights during a virtual roundtable
> with Ben Barker and others.  We published the roundtable in [1].
>
> I later interviewed Ben and Scott Bradner to learn more details. The
> interview [2] is attached.
>
> In the process of checking, Alex McKenzie sent me a more recent article
> Dave Walden, he and Ben wrote which covers several incidents related to
> reliability, and he sent a reference to the article to the list.  See [3]
> below.  I also learned that Ben passed away two years ago.  I'm sad.  He
> was a delightful and always positive guy.
>
> After further discussion with Alex, we agreed [1] has the least detail.
> [3] is best, but it's behind a paywall.  The interview [2] is a
> close second.
>
> I think this is all the information that's available.
>
> Thanks to Ben for the delightful story, to Geoff for asking for the
> details, to Scott for permission to use the interview, and to Alex for the
> recent article and advice on how to proceed.
>
> Steve
>
>
> [1]  "The Arpanet and Its Impact on the State of Networking," Stephen D.
> Crocker, Shinkuro, Inc., Computer, October 2019.  This was a virtual
> roundtable with Ben Barker, Vint Cerf, Bob Kan, Len Kleinrock and Jeff
> Rulifson.  Ben mentioned the problem with the IMP lights.  It's only a
> small portion of the overall roundtable.  The next two references have more
> detail.
>
> [2] "Fixing the lights on the IMPs," an unpublished interview with Ben
> Barker and Scott Brader, 3 July 2020.  It's attached.
>
> [3] "Seeking High IMP Reliability in the 1970' ARPAnet" by Walden,
> McKenzie, and Barker, published in Vol 44, No 2 (April - June 2022) of IEEE
> Annals of the History of Computing.
>
> ---------- Forwarded message ---------
> From: the keyboard of geoff goodfellow <geoff at iconia.com>
> Date: Mon, Aug 18, 2025 at 8:54 PM
> Subject: Re: [ih] Nit-picking an origin story
> To: Steve Crocker <steve at shinkuro.com>
> Cc: John Day <jeanjour at comcast.net>, Dave Crocker <dhc at dcrocker.net>,
> Internet-history <internet-history at elists.isoc.org>, <dcrocker at bbiw.net>
>
>
> [I] am innately curious about the ARPANET "The IMPs Lights Reliability
> Issue" you mention here and wonder if some additional color could be
> elucidated to the colorful story as to just HOW "the lights on the IMP
> panel being a major source of outages" and specifically what
> "re-engineering" was effectuated to ameliorate them from crashing the IMPs?
>
> On Mon, Aug 18, 2025 at 7:22 AM Steve Crocker via Internet-history <
> internet-history at elists.isoc.org> wrote:
>
> > ... Ben Barker has a colorful
> > story about the lights on the IMP panel being a major source of outages.
> > The IMPs had a 98% percent uptime at first.  98% was astonishingly good
> > compared to other machines of the day, but intolerably poor in terms of
> > providing an always available service.  Ben re-engineered the lights and
> > brought the reliability up to 99.98%.  How's that for a small thing
> having
> > a big effect!
> >
>
>
> Sent by a Verified
>
> sender
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