Neat trick for peps with japanese machines.

[Vic Viper]

I just did something this evening with the Snatcher ISO that might be of interest to you all who own a japanese Mega-CD (Any model). I replaced the original US/C security code on the beginning of the iso with the J code and aded some NOPs to pad the size to the same of the american code, killing the gap caused by the diference of size. That made the game work in my Meca-CD directly with the original bios (my machine has a custom made "multibios" with US and Japanese bios). This lazy bun regrets for drilling his precious Mega-CD for sake of putting a selection switch.

How it was done :

Original code J > 156h (342 bytes)

US/C code > 584h (1412 bytes)

The japanese code was paded by adding 535 NOP instructions

so it fit the original boot code that starts 1070 bytes ahead from where the japanese "security" code ends.

I don't know if anyone else tried that already(US/Euro to JAP), but making a automated tool for doing that simple job seems to be the logical next step.

 

[Artemio Urbina]

There is an automated tool to do taht already, but quite good you found that on your own. Doesn't work with all games though.

 

[Vic Viper]

Artemio, can you tell me which games doesn't work with this trick and what is the name of the automated tool ? I really want to give it a try ....

 

[King M]

the program is scdconv, available at eidolon's inn, and there is a compatibility list somewhere over there too.

 

[Vic Viper]

SDConv doesn't do conversions to JAP.

It does: (directly from it's readme)

SCDConv v2.50 - © 1999 by Eidolon - http://eidolon.psp.net

------------------------------------------------------------

- conversion American -> European

- conversion European -> American

- conversion Japanese -> American

- conversion Japanese -> European

Planned for future release:

- conversion American -> Japanese

- conversion European -> Japanese

So people with Japanese machines are left to the dust, waiting for the future version ...

Everything I tried with "my hack" so far worked flawlessly on my japanese MEGA-CD

 

[Artemio Urbina]

that is great news my friend. If you have all documented, we can easily write a toold for the purpose.

 

[Vic Viper]

Actually I have everything documented. As it's pretty simple, should be no trouble to put my "quick and dirty" nops or a relative jump instruction on the end of the japanese security code for the correct address on the IP.BIN of the iso.

The method I used was:

I'd pad size of the japanese security code with 68000 opcode NOP.Then I inserted Japanese security code on the IP.BIN, overwritting original Euro/US code.(IP.BIN previously read with CDRWIN to get the 1st 15 sectors only).After patching the IP.BIN, I inserted it on the ISO using the infamous echelon ipinsert tool. After that, I could make Snatcher boot directly on my japanese Mega-CD without any trouble. Since there's absolutely no code relocation, all US/Euro games should work perfectly on a japanese machine. Exept for a nasty megadrive language bit check, or if the game do check the bios version or header ...