That's because Cray's didn't have MMUs much less paging functionality. All the jobs required manual shuffling around and even a certain amount of explicit bound

That's because Cray's didn't have MMUs much less paging functionality. All the jobs required manual shuffling around and even a certain amount of explicit bounds checking. Essentially they were batch Fortran machines, CDC6600+++ with larger memories with modern-ish OS hacked onto them.