How does TMSS work with licensed games that predate TMSS?

Discussion in 'General Sega Discussion' started by flarn2006, Jan 3, 2018.

  1. flarn2006


    SA2 Cheat Table
    According to this page, the game needs to be specifically programmed to write the string "SEGA" to a specific memory address. On an older Genesis that doesn't have TMSS, this will cause a crash unless the code specifically checks the hardware revision first. So, what about cartridges that were made before TMSS was invented? Clearly they wouldn't be programmed to check if they're running on a console that hadn't been invented yet, and perform a specific step necessary to make it compatible with a behavior of said system that also hadn't been invented yet. So if you attempt to use a pre-TMSS cartridge, for an officially-licensed game, on a TMSS Genesis, it wouldn't find the string there, right? How does it know the game is in fact licensed if it doesn't write the string?
  2. Black Squirrel

    Black Squirrel

    staying alert on the beach Wiki Sysop
    Northumberland, England
    quipu two metres apart
  3. GerbilSoft


    RickRotate'd. Administrator
    IIRC all licensed titles have the TMSS check. It was apparently part of the development kit before it became part of the hardware for some reason.

    There's a few early unlicensed titles that don't have TMSS. (I think some were by EA.)
  4. Mentski


    Pff. Member
    Parts Unknown
    Being a mysterious face.
    90% of Japanese Mega Drive 1s (from VA0 to at least VA6) don't have TMSS at all. Everything runs fine in them. With the TMSS check absent the cart will boot regardless of what is (or isn't) written in those memory locations. AFAIK.

    A few early '89 Japanese cartridges (and a couple of EA games probably made before Sega and EA came to an arrangement... So to all intents and purposes, were unlicensed) won't run on post-TMSS revisions because they don't put the code where the TMSS boot ROM expects it. but it's only a handful.

    Thankfully for those Japanese games, a Japanese console didn't check anyway so they ran just fine. A bit of a bummer for anyone unlucky enough to import one for use on a later Genny or PAL MD though. I believe EA made revised versions of their titles that had the TMSS code missing.

    It wouldn't. If the string isn't there and and the console has TMSS, it simply won't run. But as the article in Sega Retro says, the TMSS standard was set as early as mid-1989, before the Initial US release in August.

    So basically, all licensed western carts would've been TMSS-compliant on day 0, despite the fact that TMSS-enabled consoles didn't turn up for a year or two after.
  5. flarn2006


    SA2 Cheat Table
    Interesting! Thanks for explaining. :)