> On Jul 22, 2024, at 10:14 PM, dwight via cctalk <cctalk@classiccmp.org> wrote:
>
>
> Bob Rosenbloom started to make a relay computer, using pc boards, but found
> that typical dip relays talk to each other ( leaky magnetic fields ) .
> Konrad Zuse made several attempts but making useful electromechanical memory
> was his down fall.
Clearly it an be done, considering Mark I as an example.
It's also possible to get into a lot of trouble if you aren't skilled enough.
A beautiful example is the ARRA computer designed in Amsterdam around 1950. It
was a relay machine, asynchronous (no clock; the designers were theoretical
physicists who didnt know about such things). Perhaps the worst mistake was
that they used relays that for some reason had two coils, and figured they
could use that to treat the relay as an OR gate.
In the end, they got it to work well enough to run a program once, at the
official opening of the lab. To minimize risk they made it a random number
generator program. :-) But that was the end of it. So they hired a student
of Aiken and built an entirely different machine (with vacuum tube logic, no
relays), called ARRA II to make it appear to be just an upgraded ARRA.
It's interesting that the designers of ARRA spoke about what they did, and were
quite honest about their mistakes. Quite refreshing. Unfortunately that
narrative is in Dutch: "Computers ontwerpen, toen".
https://ir.cwi.nl/pub/13534/13534D.pdf One of these days I should finish my
translation of that lecture.
paul
