Having started in 8-bit microcomputers and progressing to various desktop platforms and servers, mainframes were esoteric hulking beasts that were fascinating but remained mysterious to me. In recent years I've started expanding my appreciation of classic mainframes and minis through reading blogs and retro history. This IEEE retrospective on the creation of the IBM 360 was eye-opening. https://spectrum.ieee.org/building-the-system360-mainframe-n...
Having read pretty deeply on the evolution of early computers from the ENIAC era through Whirlwind, CDC, early Cray and DEC, I was familiar with the broad strokes but I never fully appreciated how much the IBM 360 was a major step change in both software and hardware architecture. It's also a dramatic story because it's rare for a decades-old company as successful and massive as IBM to take such a huge "bet the company" risk. The sheer size and breadth of the 360 effort as well as its long-term success profoundly impacted the future of computing. It's interesting seeing how architectural concepts from the 360 (as well as DEC's popular PDP-8, 10 and 11) went on to influence the design of early CPUs and microcomputers. The engineers and hobbyists creating early micros had learned computers in the late 60s and early 70s mostly on the 360s and PDPs which were ubiquitous in universities.