[TUHS] off-topic: resurrecting the IMP

[Armando Stettner]

THIS IS SO COOL!!

  aps at dec-marlboro
  aps at rand-ai


Begin forwarded message:

> From: Aharon Robbins <arnold at skeeve.com>
> Subject: [TUHS] off-topic: resurrecting the IMP
> Date: December 1, 2013 1:18:26 PM PST
> To: tuhs at tuhs.org
> 
> Hi all.
> 
> This may be of some interest.  From a friend at Utah:
> 
>> Date: Sat, 30 Nov 2013 16:06:25 -0700 (MST)
>> Subject: [it-professionals] computer history: Arpanet IMPs resurrected
>> 
>> The simh list about simulators for early computers recently carried
>> traffic about an effort to reconstruct and resurrect the Arpanet
>> Interface Message Processors (IMPs), which were the network boxes that
>> connected hosts on the early Arpanet, which later became the Internet.
>> 
>> There is a draft of a paper about the work here:
>> 
>> 	The ARPANET IMP Program: Retrospective and Resurrection
>> 	http://walden-family.com/bbn/imp-code.pdf
>> 
>> Utah was one of the original gang-of-five hosts on the Arpanet, and we
>> received IMP number 4.  Utah is mentioned twice in the article, and
>> also appears in the map in Figure 3 on page 14.
>> 
>> One amusing remark in the article (bottom of page 7) has to do with
>> the fail-safe design of the IMPs:
>> 
>> 	In addition ``reliability code'' was developed to allow a
>> 	Pluribus IMP to keep functioning as a packet switch in the
>> 	face of various bits of its hardware failing, such as a
>> 	processor or memory [Katsuki78, Walden11 pp. 534-538]. This
>> 	was so successful there was no simple off switch for the
>> 	machine; a program had to be run to shut parts of the machine
>> 	down faster than the machine could ``fix itself'' and keep
>> 	running.
>> 
>> As happened with early Unix releases, machine-readable code for the
>> IMPs was lost, but fortunately, some old listings that turned up
>> recently allowed its laborious reconstruction, verification, assembly,
>> and simulation.
> 
> Arnold
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