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Thread: [GUIDE] Make a Reprogrammable Genesis Cart

  1. #76
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    It's me again.
    I've tried piggybacking 3x27c322 in order to gain a 12MB game. The problem is that only the first EPROM is being loaded, no switching happens here. Here's my setup for the 74LS139:

    Pin 01 - /CE (cart connector)
    Pin 02 - A21 (cart connector)
    Pin 03 - A22 (cart connector)
    Pin 04 - /CE of ROM 1
    Pin 05 - /CE of ROM 2
    Pin 06 - /CE of ROM 3
    Pin 07 - NC
    Pin 08 - GND
    Pin 09 - NC
    Pin 10 - NC
    Pin 11 - NC
    Pin 12 - NC
    Pin 13 - VCC
    Pin 14 - VCC
    Pin 15 - VCC
    Pin 16 - VCC

    This also happens when only 2x27c322 are connected.

    What is wrong here?

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    Hi,

    I bought some M27C800 chips in order to make some repros. I don't really understand which pins do I have to wire. I've soldered all the pins except A18. I've burnt a 1MB ROM on my 1024k EPROM, with success. But somewhay the game doesn't boot. I don't even have the Sega license panel.

    The donor cartridge contained a 1024k ROM on it. So from what I've understand, I only had to solder all the pins except A18.

    Did I miss something ?

    Thanks for your help

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    A18 has to be connected to cartridge connector B7 if there's no connection to the board.
    Otherwise the game can't boot.
    See first post for details (down below).

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    Hi, first nice job there!

    I'm thinking to get started on this cartmod thing, and I have some (really noob) questions:

    First i want to know which eprom writer i buy, every one talks about willem and it is very cheap (which is good) but i want to make some phantasy star iv translated to my language, and everybody says willem is not reliable on writing on big eproms.

    Also i want to know, since the mod will aways be on a cartridge of the same game, will i need to make jumps on the eprom?

    Will be a problem on using a bigger eprom than the rom? like a 32Mbits for a 8Mbits game.

    Sorry my poor english, this is not my native language.

    Thanks!
    "Well, let's just turn this SH** on and see what happens!" - Some friend of mine.

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    First i want to know which eprom writer i buy, every one talks about willem and it is very cheap (which is good) but i want to make some phantasy star iv translated to my language, and everybody says willem is not reliable on writing on big eproms.
    Willem is not always bad, I would call it intermittently bad. Sometimes they work and sometimes they do not. If you have the money, buy a GQ-4x.

    Also i want to know, since the mod will always be on a cartridge of the same game, will i need to make jumps on the eprom?


    Most often, no. If the Donor cartridge is smaller than the new game, then maybe.


    Will be a problem on using a bigger eprom than the rom? like a 32Mbits for a 8Mbits game.
    No problem.

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  7. #81
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    HI, first let me just say thank you for all the excellent info. So what I would like to do is make a cart that I could flash any game on it. I have some spare 27c322's laying around that I can use. So is it possible to have one cart support any game? What I was thinking is getting a 32Mbits donor cart with battery back and maybe adding a switch to enable/disable the battery. Would this be possible or am I missing something?

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    Enabling/Disabling the battery via switch is possible, however, you will need to do this with the decoders as well, iirc.
    A 27C322 can be used on any game with the proper wiring. However, you cannot use a battery backed up game on a basic board e.g. Sonic the Hedgehog, unless you don't want the game to save.

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    Quote Originally Posted by xIceMan View Post
    Enabling/Disabling the battery via switch is possible, however, you will need to do this with the decoders as well, iirc.
    A 27C322 can be used on any game with the proper wiring. However, you cannot use a battery backed up game on a basic board e.g. Sonic the Hedgehog, unless you don't want the game to save.
    So if the game does not require a battery back up, and the donor cart has a battery does it have to be disabled? Also if I understand it correctly on a 32Mbit cart all the pins are already connected so if using a game that is less then 32Mbit is their rewiring have to be done. And if so can this be avoided by mirroring the game to equal 32Mbit?

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    The problem is that there are many different types of games. Some use SRAM to save, some use FRAM and some use Serial Flash RAM. SRAM requires a battery, FRAM does not and serial RAM requires a much different hardware setup. Theoretically you could have two boards to support 'most' ROM images. One could support 2MBytes of ROM and 32KBytes of RAM and the other board could contain 2MBytes of ROM and 4KBytes of Serial RAM.

    Read my teardown of different saving techniques:
    http://jazz-disassemblies.blogspot.c...is-saving.html

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    Hi Jazz! Got a quick question for you about rewiring eproms to fit smaller size boards (27C322 on a 2MB board, for example). Obviously, A20 needs to be rewired, and it supposedly goes to 'B9' according to your 1st post:
    Is this referring to board hole #9, or B9 traced out from the left on the contact pins going into the Genesis?
    Also, do I need to bend A20 so that it does not make any contact on board hole #20 or does it not matter?
    Lastly, if I want to change the region of a game, I heard a rumor I can change one bit in the hex code using a hex editor, but have no idea what bit to change. I tried using a region swapper program and my Genesis didn't like it, lol.
    Thanks a lot for your help! Because of it, I've been able to get one to one sized games created with no problem!

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    B9 can be found on the cart's edge:
    Spoiler warning:





    You will only have to pull up your EPROM's A20 if it is connected to something on the board. You may either cut the trace from it, or pull it up.

    Yes, you can change regions within the header of a ROM like so:

    Spoiler warning:





    Check the ROM in your emulator by forcing it to your region without auto-detect enabled.

    Cheers

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  14. #87
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    Thank you VERY much! I was able to get a few carts done using this method, but are eagerly awaiting my 160 chips so that I can go 1 for 1. It's funny how much easier Genesis repro carts are to do than SNES or NES repros.

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    Hi,

    I have many donor boards with batteries but the games I want to burn don't need the batteries.

    Is it possible to bypass the battery ? Can I route my pins like on a normal board or do I need to solder some other pins ?

    I also have a ferromagnetic savetype board on which I intend to put Megaman The Wily Wars. What do I have to consider in order to make the game usable ?

    I'm also interested in bank switching. I plan to do a Thunder Force III & IV compilation. Can I use the same switching method as on the M27C800 in order to switch from two 1024kB banks on a M27C322 chip ? What would be the easiest way to make this compilation ?
    Last edited by bimmywhammy; 4th-November-2014 at 13:06.

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    hi guy´s

    i had burned some 27c400 on my willem but aparently on carts without batery ,just have success on the dizzy game and speedball ,other 512k games doesn´t seem to boot ,neither normal nor swap byte.
    Could it be because of the region Rom´s ?
    I am on Portugal and our megadrives or genesis as you call ,is pal 50 hz.
    And if so how can i be sure that the rom is europe ,to burn them ok?

    Regards

    JOSÉ

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    Quote Originally Posted by bimmywhammy View Post
    Hi,

    I have many donor boards with batteries but the games I want to burn don't need the batteries.

    Is it possible to bypass the battery ? Can I route my pins like on a normal board or do I need to solder some other pins ?

    I also have a ferromagnetic savetype board on which I intend to put Megaman The Wily Wars. What do I have to consider in order to make the game usable ?

    I'm also interested in bank switching. I plan to do a Thunder Force III & IV compilation. Can I use the same switching method as on the M27C800 in order to switch from two 1024kB banks on a M27C322 chip ? What would be the easiest way to make this compilation ?
    For the first question, you can simply ignore the battery altogether.
    For the FRAM, you will have to find the "SRAM hack" for Mega Mean Wily Wars. The game originally was released for Serial-eeprom RAM.

    If you want a compilation of two games that save, you will also have to use the switching method to bank-switch the RAM as well, so they do not overwrite each other's save files. You can do this with a single switch and a bigger SRAM IC to switch out the old one with. Or you could do it with logic ICs and have the ROM/RAM switch with the click of the reset button.
    My option
    Another option

    Quote Originally Posted by ramparts View Post
    hi guy´s

    i had burned some 27c400 on my willem but aparently on carts without batery ,just have success on the dizzy game and speedball ,other 512k games doesn´t seem to boot ,neither normal nor swap byte.
    Could it be because of the region Rom´s ?
    I am on Portugal and our megadrives or genesis as you call ,is pal 50 hz.
    And if so how can i be sure that the rom is europe ,to burn them ok?

    Regards

    JOSÉ
    You can check if your ROM is USA, Japan or Europe buy looking at the header information.
    Download a Hex editor (I prefer HxD) and then read this post:
    http://www.epforums.org/showthread.p...68#post1774268
    In that post, I show how to make any ROM region free.

    You always have to swap byte. I suspect that an address pin may be left floating, or you put the ROM in the socket wrong.
    Did you place the ROM all the way to the "right" of the socket?
    Look here closely;

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