Did you know that in addition to being Sega’s first console, the SG-1000 was also used as the basis for some of its arcade games? I put out a new blog post this weekend, but it turns out these arcade games– enhanced versions of Champion Boxing, Champion Pro Wrestling, and Doki Doki Penguin Land— can be played on the home systems as well! Check out the blog post for full details or a quick summary here.
The secret lies in the memory map. All of the arcade games use all 48kiB of the system’s available ROM space; in some home games, parts of this space are used for RAM instead. With a simple AND gate, you can build a cartridge with the following mapping:
This 48kiB space should be sufficient for all of the arcade games. I imagine an Everdrive, if one existed for the SG-1000, could easily handle this. Unfortunately, there’s another issue that will come up which an Everdrive can’t solve; either a code change or a hardware mod is necessary:
The game will want you to insert a coin and press start. Unfortunately, the SG-1000 does not have a coin input or a start button. For the arcade, the start buttons map to buttons otherwise used by player 2: this approach of modding will only produce a console capable of playing single-player games. There are actually two unused inputs on a 74LS257 used to read the controllers; adding buttons to these points will create COIN and TEST inputs. This is IC9 on my SG-1000 II, but will be a different chip on the original model.
With that completed, you can insert coins, and play arcade games on your SG-1000! I haven’t been able to get these to work on the Master System as of yet; if they did, they would have the off compatibility palette, so I’m not sure how desirable that would be. Overall, the SG-1000 arcade games aren’t anything special; they’re all ports of games that got standard releases. But it’s fun to see this oft-forgotten bit of Sega history and expand the SG-1000 library just a little.