I had a professor in college teaching computer systems and design. Somehow he got to talking about the NSA. He said that back in the 60s, the NSA had computers that were running at 1000. “1000?” I asked, wondering if he’d forgotten the units. He replied “Yes, 1000.”
The professor is incompetent because he doesn't actually know how to talk about the performance of computers. It's not really a "joke", more of an anecdote
I heard from a group of teachers (my mother was a teacher) that were at our house once. "Those who can, do; those who can't, teach; those who can't teach, administrate."
"Those who can, do; those who can't, teach; those who can't teach work here."