Like today’s Intel-AMD duopoly, the market for home computer CPUs in the 1970s and ’80s was dominated by two players: Zilog with their Z80, and MOS Technology with their 6502 processor. But unlike today, even if two computers had the same CPU, it didn’t mean the two were software compatible: differences in memory layout, video interfaces, and storage media meant that software developed for an Atari 2600 wouldn’t run on an Apple I, despite the two sharing the same basic CPU architecture.
[Augusto Baffa]’s latest modern retrocomputer design, the Baffatari 2600, cleverly demonstrates that the difference between those two computers really is only skin-deep. The Baffatari is a plug-in board that adds Atari 2600 functionality to [Augusto]’s earlier Baffa-6502 system, which was designed to be Apple I-compatible. Since both the Apple and the Atari are powered by 6502 CPUs, only a few peripherals need to be swapped to change one into the other.
Sitting on the Baffatari board are two chips essential to the Atari 2600’s architecture: the 6532 RAM I/O Timer (RIOT) that contains the RAM and joystick interface, and the Television Interface Adapter (TIA) that handles the graphics and audio. These chips connect to the Baffa-6502’s system bus, enabling the main CPU to communicate with them and run Atari 2600 software titles. In the video embedded below, you can see several classic games running on the Baffa system.
The basic idea is similar to this RC2014 plug-in board that enables a Z80-based retrocomputer to run MSX and Colecovision titles. In fact, [Augusto] also built such a board for his earlier Z80 project.