Melinda Varian has a very interesting site, including stuff about IBM’s VM systems, including the Personal/370. Also, some travel. 🙂
It’s interesting to study these systems, because of how lean and mean they are. Screwed up by modern architecture measures, and often written in assembly language, they still contain interesting ideas. (I still enjoy reading about VAX/VMS process and memory management internals, and “strange” systems like the Transputer. It’s a breath of fresh air from the ambient Unix / Windows / Intel stuff).