Running Wozmon on an Old Atari 2600

Steven Wozniak was just as important to Apple Computer’s early success as Steve Jobs was — arguably even more so. While Jobs was an undeniable genius when it came to business and understanding consumer demand, Wozniak was responsible for the actual engineering. He developed the Apple I computer by himself and programmed Wozmon to run on the Apple I’s MOS 6502 processor. The Atari 2600, like many other famous 8-bit systems from the era, also contained a 6502 processor and that let Johannes le Roux run Wozmon on the console.

While it is largely a coincidence attributable to the small scale of the early computing scene in Northern California, Steve Jobs worked at Atari before starting Apple. As the story goes, Steve Wozniak let Jobs borrow a homebrew version of Pong that he built. Jobs took that to his interview at Atari and they thought the design was Jobs’s, which got him the job. Later, Jobs partnered with Wozniak to sell the Apple I computer in 1976. Then in 1977, Atari released the Atari Video Computer System (VCS) that would later be renamed the Atari 2600. While it was primarily marketed as a video game console, the Atari 2600 had similar specifications to home computers of the time (including the Apple I) and successors in the Atari 8-Bit Family would even include built-in keyboards.

The Apple I had far more RAM than the Atari 2600, as well as different video hardware. But the other specifications —namely the 6502 processor— are close enough for this project to work. Modern computers have several layers of abstraction between peripheral ports and the CPU/RAM, but that wasn’t the case in the 8-bit era. Johannes discovered that he could load his own assembly code by the same means as intended for booting games: through the cartridge port. That port is less like the USB ports we have today and more an interface to expand the ROM and RAM connected to the 6502 processor. Johannes was able to connect those chips to the cartridge port through a breadboard and an adapter for the cartridge port. With that, he was able to load whatever he wanted — including Wozmon.