Steve Wozniak's design of the Apple II avoided video snow by alternating access to main memory between the 6502 CPU and the video system. The two systems cannot collide and thus cannot create snow. I asked myself, "Could I do that with two CPU's?" and an obsession was born.

The design uses a multi-phase clock that alternates memory bus control between the two cores, achieving symmetric multi-processing in an 8-bit computer. There is also a "mutual exclusion" circuit that helps coordinate access to shared resources between the two cores in an atomic manner.

The rest of the computer is similar to the Ben Eater 6502 Breadboard Computer, with the same RAM, ROM, VIA, and ACIA chips. Everything else is done with standard 74HC-series TTL. No PLD's or FPGA's are required.

More information, schematics, example software, and more on my GitHub page.