[cctalk] Re: Relay computers

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