MultiMode3 Source

Post by **Hornpipe2** » July 12th, 2014, 3:19 pm

Just got a PSX from the thrift store, and now in search of a modchip. I could buy one, but prefer tinkering with PIC chips as a hobby anyway (have a programmer and some assembly experience), so I thought of burning my own.

Incidentally, someone released the source to the MM3 modchip in 2012. You can view it here:
http://www.maxconsole.com/maxcon_forums ... -released!
As I understand it, MM3 is "best of the best" in PSX modchip world. (Does it work on PS1?)

Now the fun part: the 12F629 is overkill for this application, and could be done in the smaller PIC12F508. So I'll take a crack at porting it to the smaller chip, plus I want to see how the code works! Perhaps improvements could be made to it, leading to a sort of MM3.1.

First step is proper commenting of the disassembly. I've made some headway but am somewhat unclear as to how this thing really functions. It's a stealthmode chip with internal oscillator. I think opening the door or pushing Reset will restart the sequence, and it's shut off by memory card access or countdown timer. Am I on the right track?

Post by **Shendo** » July 12th, 2014, 5:27 pm

Are you talking about PSone when you say PS1? Because PS1 means all PlayStation 1 models (fat and slim).

Yes, MM3 works on PSone but if you are using it with a PAL console
you won't be able to boot NTSC titles without a boot disc.

That's because an extra check in BIOS was added to those models.
To bypass that you need to install "OneChip" modchip which AFAIK is a MM3 with a simple BIOS patch.

Also that source you found is a port, original MM3 was made for PIC 12C508.

Personally I use a self made JDM Programmer with IC-Prog to program 12C508A chips but you can also
use 12F508 because the code is compatible.