T1lt's Sega Genesis Flash Cartridge Does What Most Don't: Plays Sega Master System Games
Clever cartridge bypasses the Motorola 68000 CPU in order to run Master System games on the Zilog Z80 coprocessor.
Pseudonymous game developer and vintage console enthusiast "t1lt" has built a flash cartridge for Sega's Genesis, with one key difference: it's designed to hold Sega Master System games instead.
"One of the little-known features of the Sega Genesis/Mega Drive is its ability to play original Sega Master System eight-bit cartridges using a special adapter," t1lt explains. "This cartridge combines the SMS to Genesis adapter circuitry with some classic Master System hardware to make an eight-bit-only flashable Genesis cart!"
Launched as the 16-bit successor to the eight-bit Sega Master System, the Genesis — known as the Mega Drive in some countries — was powered by a Motorola 68000 processor, a big upgrade over the Zilog Z80 driving its predecessor. That same chip, though, was also present in the Genesis, and used to drive its audio system — though an optional add-on would allow the console to switch to the Z80 as its primary processor game cartridges made for the Master System.
The flash cartridge designed by t1lt does away with the need for both the adapter and an original Master System cartridge, allowing the user to flash cartridge images up to 512kB in size and run them on an unmodified original Genesis. "The cartridge emulates the function of the original 315-5235 Sega Paging Chip using a novel design with 10 discrete logic ICs [Integrated Circuits], paired with a battery backed SRAM for game save," t1lt explains.
"It started as a personal project," t1lt continues, "to see if I could get Phantasy Star to run on a newly acquired Genesis, but as a homebrew developer of NES [Nintendo Entertainment System, the Sega Master System's primary competitor] games, 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."
The cartridge is available to order on Tindie at $45 fully-assembled, complete with housing; "a T48 or similar flash ROM programmer is required to program the 39SF040 PLCC flash IC on board," t1lt notes.