The idea was certainly around in the early-to-mid 1980s, when some former Intel engineers founded Sequent.

The Balance 8000, released in 1984, supported up to 12 processors on dual-CPU boards, while the Balance 21000, released in 1986, supported up to 30.

I interviewed the founder, Casey Powell, and he was explicit about multiple Intel microprocessors replacing large systems. He was targeting minicomputers at the time, of course, but we all anticipated that bigger sets of more powerful CPUs would eventually surpass even the biggest "big iron".

Powell was a great guy. However, his company got taken over by IBM. In the end, he didn't get to change the world.

"It's hard to be the little guy on the block and have really great technology and get beaten, just because the other guy is big." https://www.cnet.com/news/sequent-was-overmatched-ceo-says/