What is it?

One of the little-known features of the Sega Genesis/Mega Drive is its ability to play original Sega Master System 8-bit cartridges using a special adapter. This cartridge combines the SMS to Genesis adapter circuitry with some classic Master System hardware to make an 8-bit-only flashable Genesis cart!

On the Master System side, the cartridge emulates the function of the original 315-5235 Sega Paging Chip using a novel design with 10 discrete logic ICs, paired with a battery backed SRAM for game save.

Use this cartridge to out try out one of your original Master System games like Phantasy Star as a Genesis cartridge, or if you are a SMS developer, this could be a new 512KB platform to release your 8-bit games on.

Notes:

• A T48 or similar Flash ROM programmer is required to program the 39SF040 PLCC flash IC on board.
• SMS compatibility was removed for Genesis v3 (the one with the giant 3 on it). So get you a proper v1 or v2 unit to use this cartridge. As for other later repro's like Retrobit, etc. these are untested so definitely double-check they advertise SMS support before buying!
• This cart won't play every SMS game ever made by a long shot, but it supports some good ones.

Supported original SMS games include:

• Alex Kidd in Miracle World
• Fantasy Zone
• Galaxy Force
• Golden Axe
• Golden Axe Warrior
• Kenseiden
• Mercs
• Monopoly
• Phantasy Star
• Psycho Fox
• Space Harrier
• SpellCaster
• Wonder Boy III - The Dragon's Trap
• Ys - The Vanished Omens

Included

• PCB
• CR2032 battery
• Genesis cartridge housing
• Optional cartridge label

Features

• Battery backed SRAM with 5+ year battery life
• 512KB (4 Megabit) removable/reprogrammable flash storage
• High reliability gold cartridge contacts

Why did you make it?

It started as a personal project to see if I could get Phantasy Star to run on a newly acquired Genesis, but as a homebrew developer of NES games ( see my itch site here ), I realized there wasn't anything like it out there for SMS homebrew developers looking for a way to release their games for the Genesis as well. Feel free to reach out if you are looking for a custom version of this cartridge for a different paging chip, no battery save, different hardware configuration, etc.

What makes it special?

As far as I know this is the first 8-bit Genesis cartridge, and the first successful replacement of the proprietary Sega 315-5235 chip with off-the-shelf parts.