I contracted at an IBM facility in Boca Raton about 35 years ago. (not the one that made PCs. A different division that developed automation for factory floors.)

The room I was parked in was also the access for one of their active mainframes.

A guy who maintained that system told one of my office mates the following:

The VM operating system (the standard for IBM big iron) consumed 90% of the CPU resources in order to manage and dole out the remainder 10% to processes that did actual useful work such as calculations.

Just a data point on system overhead. If an MMT person got hold of this information, 9 out of 10 US residents would work for the government.