Look at the Green Arrays F18, the "conclusion" that Forth reached:
https://www.greenarraychips.com/home/documents/greg/PB003-11...
Here's a clear description of what each instruction does:
https://colorforth.github.io/forth.html
Hilariously, the system has no logical OR, only AND and XOR and NOT, because "Inclusive-or is rarely needed."
This system was designed by Chuck Moore, father of Forth. Here is an entertaining video of him explaining the F18A stack machine and programming system:
This is such a simple machine. I am planning to make a tiny emulator for my site. One could probably write an emulator in 80 lines of Go (one goroutine for each of the 144 cores).