1958 FACOM 128B Japanese Relay Computer - Page 1
Forum section: electronics / general

author: Homer J Simpson
author_rank: Super Contributor
timestamp: December 01, 2019, 11:19:57 pm
content: CuriousMarc gives some history on relay based computers then a tour of a working 1958 FACOM.

author: VK3DRB
author_rank: Super Contributor
timestamp: December 02, 2019, 09:53:45 am
content: Simpson, is that what Mr. Burns uses at the nuclear plant? Actually the output display reminded me of the Jupiter 2 in Lost in Space, or the robot with its random flashing lights.Actually the video was fascinating. I appreciate the ingenuity. It is likely the relays in the machines had "pick and hold" coils to increase latching speed, lower power consumption and reduce heat dissipation. After all, they all used linear power supplies, many with selenium rectifiers.In the video, they alluded that the algorithm for square root was similar to that used in 1970's calculators. I found the source code to my Farad 808 scientific calculator from 1976 (with a vintage TI processor in it). To calculate square root of x, it simple halved x to get y, then squared y and did a greater or less than evaluation. Based on the result it would then do a (x+y)/2, or y/2 and repeat interatively until the square of y equalled x. It could do similar for nth root of x. Brilliant!I worked on equipment using complex relay logic in my first job at IBM. Whilst it was considered that IBM's unit record was "old iron" I put my hand up to work on the old iron because it was so ingenious and fun to work down tobelowcomponent level. Myself and another IBM'er were perhaps the last engineers to be trained on unit record in the world; certainly in Australia. The machines were the IBM 557, 029, 514, 517, 519, 548, 082, 083 and a host of others. The IBM 557 was a really complicated beast. No diagnostic tools other than a circuit diagram, a DMM and the infamous dynamic timer. In those days, I not only had to diagnose a crook relay, I had to repair the relay contacts, by cleaning the static contacts and or replacing the individual silver moving contacts. Often the machines also had vacuum tube arrays as bit memory. I enjoyed it immensely. That equipment was quite challenging, especially the intermittent bugs. Things are easy these days.Hats off to the Japanese for maintaining this historic machine. All the IBM old iron was thrown out around the world, even the card punches - a crying shame and short sighted as they are worth a packet now.I sort of feel privileged and unique in that I worked on this old stuff, transistor technology, SLT, valve technology, PC motherboard electronics etc. Today I work on state-o-the art electronics design.Thanks Homie. Good find!

author: woodchips
author_rank: Frequent Contributor
timestamp: December 02, 2019, 11:07:14 am
content: If interested look for The Design of Switching Circuits by Keister, Ritchie and Washburn, published by Bell Telephone.All sorts of relay circuits including calculation.I spent many years installing Crossbar telephone exchanges, and in hindsight it was very clever, common control, fault detection and recording.

author: edy
author_rank: Super Contributor
timestamp: December 03, 2019, 01:03:25 am
content: Quote from: VK3DRB on December 02, 2019, 09:53:45 amReminds me of this...