Reverse engineered the SEGA Mega Drive


With the widespread adoption of emulators, almost anyone can start playing video games from bygone eras. Some systems are even capable of supporting homebrew games, with many having active communities still creating new games even decades later. This ease of programming for non-PC platforms has not always been so simple, however. If you wanted to develop games on a now-old console when it was still relatively new, you had to go through a lot of steps. [Tore] shows us how it would have been done with his Sega Mega Drive development kit that he built from the ground up.

While [Tore] had an Atari ST, he wanted to do something a little more cutting edge and at the time there was nothing better than the Mega Drive (or the Genesis as it was called in North America). It had a number of features that lent the platform to development, namely the Motorola 68000 chip which was very common at the time and therefore had extensive documentation. He still needed to do quite a bit of reverse engineering the system to get a proper development board working, starting with understanding how the cartridge system worked. He was able to build a memory bank that functioned as a rewritable game cartridge.

With the hard parts away [Tore] set about building the glue logic, the boot firmware that interfaced with his Atari ST, and then of course wiring it all together. He was eventually able to get far enough to send programs to the Mega Drive that would allow him to control sprites on a screen with the controller, but unfortunately it was cut short before he could develop full games. The amount of research and work to get here is incredible, though, and there may be some useful nuggets for anyone in the Mega Drive homebrew community today. If you don’t want to dig deep into Mega Drive hardware, you can create a cartridge that allows development on native Sega hardware instead.


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