Cosam—an enthusiast hardware developer in the retro gaming scene—has released their Sega Neptune PCB project, giving Sega fans the ability to make their own version of the unreleased console.
While the 32X will probably always be remembered as a controversial add-on for the Sega Genesis/Mega Drive, there was a time when Sega had planned to release a self-contained 32X+Genesis console known as the Neptune. This hardware was never released commercially and—to the best of my knowledge—no prototypes exist out in the wild, but that hasn’t stopped Sega fans from fantasizing about what could have been. Modders did eventually take matters in to their own hands, Frankensteining 32Xs with Genesis boards in custom cases, but until now it always felt like an inelegant solution to this problem.
What makes Cosam’s Neptune project stand out is how incredibly polished it looks. Their Neptune board is a single PCB, with no bodge wiring or ribbon cables in sight. The feature set is exciting too:
- An updated power circuit by Zaxour, which does require a 9V 1A power supply.
- Built-in switchless region mod.
- Integrated Triple Bypass hardware, ensuring terrific picture and sound quality.
- Sega Master System game support, with a few caveats.
- SegaCD/MegaCD hardware support.
If you’re going to try your hand at making your own Sega Neptune, there are some important things to keep in mind.
The first is that this is a very advanced project involving a lot of fine soldering work. You’ll have to supply all the components that will eventually populate the Neptune PCB and attach them yourself. That means that you have to harvest the chips from a working Genesis/Mega Drive and 32X, and you also have to harvest them from specific revisions of those designs. The project was based on the hardware found in a VA1 PAL Mega Drive 2 and VA1 PAL 32X, but the GitHub page for this project notes that it could be possible to find usable chips on other console revisions as well.
Another thing is that, because this is still essentially a 32X attached to a Genesis, it has a lot of the same flash cart limitations that unmodified consoles have. You won’t be able to run SegaCD games from a MegaSD or Mega Everdrive Pro, in-game menu support would be impossible, and Sega Master System games may be blocked from loading as well. On that note, Master System compatibility has not been thoroughly tested but original carts seem to work when attached via simple passthrough adapters. Master Everdrives and FM-capable adapters aren’t mentioned on the GitHub, so it’s possible there would be issues there too.
If this project is something you’re interested in, head over to the GitHub page for it and dive in!