Hacking Game EPROM

OldFoo · Post by **OldFoo** » Mon Nov 30, 2009 4:16 am

Basically what i'm saying is i have the means to get the work done if i just knew where to look, what to look for and what to change it to. I can then make the programmer do a checksum on the entire hex image and write that info into the last few bytes or wherever its needed if in fact it is needed on the rom eprom.

OldFoo · Post by **OldFoo** » Mon Nov 30, 2009 9:41 am

Dump the cartridge eprom (normally an m27c322)

Open it up in a hex editor (WinHex is the top one).

Got offset 0x428 and check the value there. FF = Region all, 01 = Japan only.

OldFoo · Post by **OldFoo** » Mon Nov 30, 2009 2:47 pm

Do you happen to know if the checksum needs to be changed/updated? Thanks

OldFoo · Post by **OldFoo** » Mon Nov 30, 2009 6:47 pm

xmods wrote:Do you happen to know if the checksum needs to be changed/updated? Thanks

Not on a program eprom.

OldFoo · Post by **OldFoo** » Thu Dec 03, 2009 3:29 pm

hi,

is it possible to change the regeion of all naomi cart game in this way?

I mean switch jap cart game into export game..... :smt007

Change bios every time in my cab get me stressed...... :smt010

marco

OldFoo · Post by **OldFoo** » Thu Dec 03, 2009 8:06 pm

As I was previously corrected, they are talking about the EPROM that is inside the cart. Change the code to 'Region Free' and it doesn't matter which BIOS is installed on the system.

OldFoo · Post by **OldFoo** » Thu Dec 03, 2009 11:33 pm

Imo its an ideal solution to switching bios chips in your system. The bios chips are $10/ea if you have a eprom programmer and $15-20/ea if you don't. If you break a pin you are sol. The dual bios mod is a good solution if you have the means for performing it. If there was demand for it we could have a pcb made up with all 3 of the latests bios's on it and a switch to change between them. You'd need to use smd components and a thin pcb to insure it all fit under the rom cart, but it would be easy to do, however it would be expensive to make and they'd have to retail for $60-80/ea after manufacturing costs not to mention you'd need to move at least 1000 units, and i don't think that kind of demand exists. So we are stuck with either the dual bios mod diy project, installing a 42 pin zif socket in a remote location in the mobo or just changing a couple game eproms in your collection so japan only games will work in other regions. From what i've noticed the only games that require modification are the japan only games because games compatible with other regions are also all compatible with the japanese bios, but not nessissarily all the japanese games are compatible with any of the other bios's. So anyhow the way i see theres 3 options unless you want to just stick a japanese bios in your system and be done with it, except you'll be reading japanese text for alot of game, which is not an ideal solution, unless the game only supports japanese text in which case thats your only choice.

OldFoo · Post by **OldFoo** » Fri Dec 04, 2009 10:13 am

this solution for me it is ok.....I will try to change the region of one of my jap carts....if I will be able to do it and it will work I will change all my jap cart to free region...

marco