Taking a break from ogling microscopic features in Intel’s semiconductor processors, [Ken Shirriff] is back to instead poking at decidedly macroscopic pluggable modules from the 1948 IBM 604 Electronic Calculator.
Source: [Hackaday](https://hackaday.com/2026/08/03/energizing-a-vacuum-tube-flip-flop-module-of-the-ibm-604/)