TradeMark Security System

The TradeMark Security System (TMSS) was a soft lockout of games stored in the boot ROM of the Sega Mega Drive/Genesis to ensure games which were unlicensed by Sega (and thus not receiving the Sega Seal of Quality, which was attainable through a fee paid to Sega) were not playable. Earlier versions of the console did not have this boot ROM and some earlier games not designed for the TMSS may not work in later consoles.

The legality of this system was challenged by Accolade in the court case SEGA vs. Accolade, which ruled in Accolade's favor. The verdict set a precedent that copyrights do not extend to non-expressive content in software that is required by another system to be present in order for that system to run the software.

In order for software to run on a Mega Drive/Genesis with a TMSS built in, the software must write a long word containing the ASCII string "SEGA" (all caps) to address $A14000 a short time after the Motorola 68000 resets. If the game fails to do this, the next VDP access will cause the 68000 to lock up.