I took an OS course in 2005. The professor told us we wouldn't have to consider certain classes of scheduler because "none of the real computers the university bought had 'dynamic resource allocation'". I asked what he meant by that, and he said "requests for additional (or free'ing) memory, file handles, and other non-compute resources". I asked which machines had such features, and he replied with something weird like "UNIVAXEN". It was a ridiculous course.