I just got back from dinner with 3 elderly programmers, all old-time IBMers who moved to Boca in the early PC days. They had some fascinating stories about working on machines like the IBM 650, which used drum storage. One of them talked about writing his code so the inner loop was run from the precious core memory instead of a spinning drum, so it ran at incredible speeds.
Quite a different world than we have now, working with 1GB of RAM and 100GB of hard drive space & CPU speeds above 1 GHz. I only started programming around 1980 & I felt like a newbie talking to them.