Is Parallelism a Thing?

In the nineties when parallel computing architecture started to diverge. Now super computers are effectively a bunch of linnox boxes conected together with ether net. It's hard to wrap your head around writing in parallel on a million processers and having problems that have billions of degrees of freedom, but that's what people do. I remember conversations about likwell, you know, if we'd made really simple, risked machines and fit a thousand corps on a cpu,. that seems to have largely gone away in favor of gpu - which is lesten.