Powering Up a Pluggable Module from the 1948 IBM 604 Electronic Calculator
In that awkward transition phase between electromechanical accounting systems used in the 1940s and the introduction of fully digital computers we find systems such as the IBM 604 Electronic Calculator, advertised for accounting, calculating and engineering tasks. While not capable of complex instructions, loops and other advanced features, it did use an interesting modular architecture with easily swappable modules containing a vacuum tube and associated components. Recently [Ken Shirriff] took a poke at one of these and even powered it up. This kind of pluggable system would become a staple of computer systems, as they enabled the use of modules or cards with specific functions that could be swapped and combined at will to increase system flexibility, lower costs and make repairs a snap. For the IBM 604 a total of about 1250 vacuum tubes were used, apparently all of which were found on these pluggable modules. The module that [Ken] got his hands on has a thyratron tube, which is...