Remember an ex-eastern bloc dev I used to work with telling me of his early days working with a soviet PDP-11 clone which required a logic board switch dependin

Remember an ex-eastern bloc dev I used to work with telling me of his early days working with a soviet PDP-11 clone which required a logic board switch depending on the season since the temperature affected some transistors or solder - one card worked correctly in the winter, and the other in summer.. don't recall what they did for spring/fall or if these seasons were within tolerances for both cards..