Some Questions About Hacking With MESS

[BeyondTheStatic]

So I finally got around to downloading/installing MESS, and its debugger looks great. Lots of features, and you get to see the code being executed in real time. I know some of you use MESS for hacking, so I have a few Q's...

1) Is there an option to log only newly mapped code, like in FCEUX? I won't say some cheats are impossible without this feature, but it sure does cut development time down considerably

2) Can cheats be applied while MESS is running? It would seem the newer versions have no proper cheat system, aside from files you have to edit manually. Is there some way to alter a game's opcodes from the debugger's command line (and maybe even undo them)?

3) Is it possible to save/load states while a game is running?

4) Do you know of a good tutorial for hacking games with MESS?

-BTS

[Helder]

To set a break point : bring up the debugger (`), WP ADDRESS,1,w/r

To do a trace log like the fceux kind type : trace ????.log to turn it off trace off. You can give it ???? whatever name you want.

I believe you press F12 to return to the game and the w/r in the first instruction above it obviously write or read, Pugsy or nolberto or Whipon would be the men to talk about the debugger. Also look at this old thread for HazeMD the predecessor of MESS, pugsy explain in there how to do searches and traces and the such.

get the MESSUI here http://www.progettosnaps.net/mess/links.html I use 0.141b for Genesis Hacking.

[Pugsy]

1) Is there an option to log only newly mapped code, like in FCEUX? I won't say some cheats are impossible without this feature, but it sure does cut development time down considerably

Don't understand the question as I've never used FCEUX

2) Can cheats be applied while MESS is running? It would seem the newer versions have no proper cheat system, aside from files you have to edit manually. Is there some way to alter a game's opcodes from the debugger's command line (and maybe even undo them)?

Yes, though it 'depends' on the system on how easy it will be..can be quite complicated on NES because of mapping - but dead easy on other systems.

Basically you just poke the correct CPU with the correct memory space tag which is normally 'm' for ROM cheats

so to poke a system which uses a CPU called 'maincpu' and you want to change a byte 'b' at address 123456 to 0x60 :-

You type this in the debugger:-

maincpu.mb@123456=60

3) Is it possible to save/load states while a game is running?

Shift F7 to SAVE, F7 to LOAD. "Select Position" means press a key and that will be the single character filename of the save file.

4) Do you know of a good tutorial for hacking games with MESS?

There's various hints and tips can be found in these forums and my own forums, for instance there's a basic youtube tutorial on finding RAM infinite lives for Space Invaders in MAME (same debugger as MESS) here:-

http://www.mamecheat.co.uk/forums/vi...php?f=2&t=4101

Though it's probably better just to explain what problems you are experiencing - it's a massive topic.

[BeyondTheStatic]

To set a break point : bring up the debugger (`), WP ADDRESS,1,w/r

To do a trace log like the fceux kind type : trace ????.log to turn it off trace off. You can give it ???? whatever name you want.

I believe you press F12 to return to the game and the w/r in the first instruction above it obviously write or read, Pugsy or nolberto or Whipon would be the men to talk about the debugger. Also look at this old thread for HazeMD the predecessor of MESS, pugsy explain in there how to do searches and traces and the such.

I'll give it a thorough reading

Don't understand the question as I've never used FCEUX

It just logs any new code that's been executed, probably by keeping a list of addresses and compare bytes. A Walk Thru Walls cheat is a good example of how it can come in handy. The way I do it is I turn the feature on and walk around a bit without touching any walls, keeping my eye on the log until it stops reporting any new changes. When nothing new has happened I copy the last few lines to my cheat sheet for reference, and then walk into a wall. The tracer springs into action now that something new has happened, and I use that new address as a starting point when looking at a full trace log of the event. Makes things a lot simpler.

It's the same as Geiger's Snes9x "Trace Once" feature, though with that program you can't see the code being traced as is occurs. Plus, all Snes9x versions crash for me (almost every time the cheat dialog is displayed or altered); if it was the only SNES hacking utility, I'd rather not hack SNES games at all

Yes, though it 'depends' on the system on how easy it will be..can be quite complicated on NES because of mapping - but dead easy on other systems.

I'll be starting out with SNES, going on to GB/GBA after that, and later Genesis and SMS. For NES, I couldn't ask for a better hacking utility than FCEUX (except that it crashes every once in a while, but not often enough to make me pull my hair out).

Basically you just poke the correct CPU with the correct memory space tag which is normally 'm' for ROM cheats

so to poke a system which uses a CPU called 'maincpu' and you want to change a byte 'b' at address 123456 to 0x60 :-

You type this in the debugger:-

maincpu.mb@123456=60

Great Now will this be undone when a save state is loaded? If not, is there another way to easily reverse a poke without typing it back into the command line?

Shift F7 to SAVE, F7 to LOAD. "Select Position" means press a key and that will be the single character filename of the save file.

That good to know. With FCEUX I often wish I had more than 10 quick saves...

There's various hints and tips can be found in these forums and my own forums, for instance there's a basic youtube tutorial on finding RAM infinite lives for Space Invaders in MAME (same debugger as MESS) here:-

http://www.mamecheat.co.uk/forums/vi...php?f=2&t=4101

Though it's probably better just to explain what problems you are experiencing - it's a massive topic.

Good, that means I'll have plenty to keep me busy for a while

Thank you very much for the help, guys!

[dlevere]

Here is a guide, but Pugsy says that it's outdated. It may help, though.

kelvSYC's Guide to using the MAME and MESS Cheat Engine

[BeyondTheStatic]

Yeah, I ran across that a few times during my search. It was great that someone took the time to write it, but it sucks that things had to change so drastically afterward. At any rate, some of it probably is still relevant. Thanks