@jalefkowit @cstanhope It had been at least attempted in the microcomputer world. If you bought a second 6502 for your BBC Micro (doubling your memory to 64K and increasing clock speed from 2MHz to 3MHz) then well-written software, which did everything through the OS, was supposed to work. Unfortunately, lots of software wrote directly to screen memory for performance, and that simply wasn't in the second processor's memory map.