MAMEWorld Forums - EmuChat - Re: Finding a full pacman memory map

What you want might be do-able, but it depends on exactly what you desire and how you expect these hacks to be triggered.

Are you using this on MAME? If so, it is usually easier to hack by using the debugger, by setting breakpoints that can do certain things, such as disable a ghost.

More serious hacking, like your request #2 below, might require writing new subroutines which could be patched in by either using a MAME cheat, or by revising the appropriate ROM file(s). This is more involved and also requires checksum hacks to keep the game playable in MAME. I assume you are not wishing to burn new ROMs to insert into a real pacman PCB.

You want to "Disable each ghost individually". What do you mean, exactly? Do you want a ghost, when disabled, to not move in the maze at all? Or disappear? When disabled, will the ghost still turn blue when an energizer is eaten? how do you expect to trigger a particular ghost to be disabled, by pressing either or both of the start buttons? If using a MAME cheat, separate cheats could be created to disable a particular ghost, and the could be enabled via the cheat menu.

You want to "Switch between scatter and chase at will (and stop the automatic switching between them)." While related, these are two separate things. Stopping the automatic switching would be fairly easy, I think, but which mode do you want the ghosts in by default? Scatter? Or do you want it, say, when the cheat is enabled, to just keep the ghosts in whatever mode they are currently in? As for switching "at will" between modes, how do you want this to be triggered? pressing the player 1 button perhaps? Or do you want this also to be triggered by a MAME cheat which you can enable via the cheat menu?

edit:

here are mame debug build console hacks to do your request #2, using the P1 start button to trigger the mode change. Enter these in the mame debugger after loading pacman:

Code:

bp 0e3e,1,{a=7 ; g}
bp 0e40,{(b@5040 & 20) == 0}, {a = b@4dc1; pc = 0e5e; g}

The result of these hacks is that the ghosts never change from chase to scatter or from scatter to chase, unless the player presses the P1 start button. Be careful and press the button very quickly. It is easy to hold the button down too long and end up doing 2 quick reversals, which end up doing nothing.

Also be aware that the original game code prevents any mode changes from taking place while an energizer is active. This behavior is retained, and the P1 button will have no effect when any ghosts are edible.

Don Hodges

> I want to demonstrate pacman as part of a talk about AI, and thought it would be nice
> to demonstrate the ghost's behaviour in depth.
>
> To do this I would like to be able to:
>
> 1) Disable each ghost individually.
> 2) Switch between scatter and chase at will (and stop the automatic switching between
> them).
>
> I'm sure this is possible with MAME cheats. After some googling I can't find anyone
> who has described the memory layout in enough detail to do this. I just wondered if
> anyone either knows this, or knows how to find it, before I start trying to do it
> myself.

Edited by Phantom DJ (07/21/13 08:34 AM)