A selling point of the Mega Drive was that it is backwards compatible with its predecessor the SEGA Master System, at least, electronically.
Physically the ROM cartridge ports were very different in size so there was no way to play a Master System game on the Mega Drive. Enter the 'SEGA Master System Converter', also known as the 'Power Base Converter'.
Once connected to the Mega Drive the Master System Converter allows users to insert Master System cartridges into a port under the top cover as well as run Master System card based titles through the forward facing slot. Like the original Master System (not the Master System II) the card port supports use of the 3D glasses. The converter also replicates the Master System's 'Pause' button which is not natively part of the Mega Drive.
The Mega Drive incorporates the Master System's Zilog Z80 chip as a coprocessor and when a Master System game is run the Mega Drive switches to the Z80 and puts its 68000 processor into an idle state. While the Master System Converter does have some components and is more than just a pin converter, it does not contain any specific Master System smarts and is in effect a passive, hand holding affair.
The Master System Converter pictured below was designed for the original Mega Drive shell and is not compatible with the Mega Drive II. A redesigned version was created for the Mega Drive II but it did not include the Master System game card port and was only released in Europe in greatly reduced numbers.
|Unit pictured has been sold and its location is unknown.|