MAMEWorld Forums - EmuChat - Re: How do I (is this even possible?)...

> One of my primary uses of MAME is to compare MAME to a real boardset for diagnostic
> purposes.
>
> One thing I find myself wondering, is it possible to remove a given RAM from a game
> and try to run it in MAME to see how it behaves without that RAM?
>
> For example, hypothetically, suppose a real boardset has a 2114 RAM in physical board
> locations A1, B1, C1 & D1.
>
> Is it possible in MAME to "remove" the 2114 RAM at A1 and see how the game behaves?
> If so, how do you do this?
>
> Another one is Atari (and many other manufacturers) often use EAROMs to save high
> scores and operator settings. Is it possible to run the game without the EAROM in
> place? If so, how?
>
> Joe (joemagiera at ameritech dot net)
> [email protected]

Probably not without editing and recompiling the source code. MAME is still in its infancy regarding modular devices, with only certain drivers having such a thing; it's much more common for a driver to still have fake "dip switches" or machine configuration toggles with several hard coded options which were known to be valid on real hardware, and with no real concept of emulating faulty hardware such as bad RAM or a mandatory device left unconnected. In some cases, MAME's emulation is too high-level (in before MAME-haters say MAME is already too slow!) so things like out-of-spec voltages, bad capacitors or faulty glue logic (e.g. 74xx chips) causing random errors won't show up in MAME.

Emulating a dud ROM is easy though, it's a simple case of creating a 0-byte file and renaming it to match the corresponding ROM file. For example, if you're emulating a failed ROM in Centipede and the zip is located in mame\roms\centiped.zip, put the dud file in the mame\roms\centiped folder (create the folder as it most likely won't exist) and MAME will read that instead. Also works for ROM hacks and newly-dumped games that use the exact same hardware e.e. ROM swaps. In this instance, you can only use MAME from the command line as the MAME interface will refuse to load an "incorrect" ROM.