Battery backed memory support in Triple Play Gold

[Former user]

Original issue 407 created by markmartinfan86 on 2015-02-17T06:56:03.000Z:

I have been wondering about the emulation of a certain game for a while...

Triple Play Gold for the Genesis. It's an EA game that used an internal battery (I'm sure this isn't the only one to do so) to save created players, season progress etc. Every dump of it I have, on every emulator I've tried (including gens plus gx), does not recognize the memory. In other words, if you try to create a player it won't save and it won't let you play a "season" either.

If you do the button combo to reset the games' internal memory (A+B+C at the title screen), it says the battery memory is unusable.

My question is, Are these just bad dumps of the game or is there a way for the emulator to emulate the battery memory?

[Former user]

Comment # 2 originally posted by ekeeke31 on 2015-02-17T13:06:09.000Z:

That game does not seem to use different sort of backup memory than other games, just slightly larger (32KB SRAM mapped to $200000-$2FFFFF).

What it does different though is that it uses a 4MB ROM which is therefore mapped to the whole cartridge area ($000000-$3FFFFF) but also overlaps with the SRAM area ($200000-$2FFFFF).

Large games that do this usually have some kind of mapper to switch between ROM and SRAM in the area where they overlap but this game doesn't, instead it simply puts unused data in the ROM area that corresponds to SRAM area.

It does not work properly in emulators probably because they prioritize ROM over SRAM in this area.

That's what Genesis Plus GX does at least, which is a mistake (I think it was not the case in older versions, SRAM had priority over ROM in such case and was enable by default on startup)

[Former user]

Comment # 3 originally posted by ekeeke31 on 2015-02-17T13:06:27.000Z:

[Former user]

Comment # 4 originally posted by ekeeke31 on 2015-02-17T13:22:50.000Z:

To be more correct, Triple Play Gold has two ROM chips, 1 x 2MB ROM mapped at $000000-$1FFFFF and 1 x 1MB ROM mapped at $300000-$3FFFFF while 32KB SRAM is mapped at $200000-$2FFFFF (mirrored every 64KB since this is 8-bit SRAM mapped to odd address only).

So basically, ROM and SRAM don't overlap but the guys who dumped the available ROMs had the SRAM data dumped in the middle, which emulators mistake for ROM data.

[Former user]

Comment # 5 originally posted by markmartinfan86 on 2015-02-17T20:35:16.000Z:

I thank you for taking the time to look in to this.

So with the ROMS dumped the way they are does that mean the SRAM will never work in the emulator, or is there a possibility of it working in the future?

[Former user]

Comment # 6 originally posted by ekeeke31 on 2015-02-18T07:23:23.000Z:

No, this is easily fixable

[Former user]

Comment # 7 originally posted by ekeeke31 on 2015-03-02T20:46:08.000Z:

Fixed in r939

[Former user]

Comment # 8 originally posted by markmartinfan86 on 2015-03-02T22:52:23.000Z:

I just loaded up the game and it works perfectly!

Thank you for fixing this issue.