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Thread: [GUIDE] Make a Reprogrammable Genesis Cart

  1. #31
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    Place the Flicky ROM all the way to the right, meaning towards the capacitor (in my photos)? This would leave 1 and 42 on the PCB open, if that's what you mean.

    I'm quite certain the cartridge is clean and I've considered the possibility of the mask ROM having been toast too, although I think it's the most unlikeliest scenario. I can change the capacitor although it doesn't look bad. Thanks for the speedy reply, I appreciate it.

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    Quote Originally Posted by fahlim003 View Post
    Place the Flicky ROM all the way to the right, meaning towards the capacitor (in my photos)? This would leave 1 and 42 on the PCB open, if that's what you mean.
    Correct.

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    Looks like I have a problem here. I was trying to burn Oh Mummy on a 27C160 (it verified and gave me no errors). However, after soldering the EPROM to the PCB (ROM was 1MB) I lifted A19 and connected it to cartridge connector B8. The bios screen shows up, after that the game freezes and rarely get to the next screen, then freezes. I first thought I did something wrong, so I burned it another time, verified again, checksum is also fixed. Same error again. Keeps crashing (in all regions). Is this a known bug or is there some kind of bankswitching/protection going on?

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    Can we get a photo? Also, where does pin 32 of your 27c160 lead to?

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    Will take a photo after work. Pin 32 goes to BYTE/VPP. Was not lifted but inserted directly to the PCB.

    Here's the promised photo. Also A19 isn't touching any left over pins. I was just too lazy to remove them yet. IMG_2062.jpg

    Tried burning the ROM on a 27C322 (bent up A19 and A20) on a 1MB PCB. Connected them to B8 and B9. Same glitch. I'm now pretty sure it's the game using some protection/bank switching, since other games work fine.

    Sorry for the triple/quadruple posting but I'm interested in another project and I don't want to make a new thread for every post since it all related to custom cartridges. I've seen a few games that are 8MB or larger and thus not fitting in one 27C322. Is it possible to burn such a game to 2x27C322 using a 74LS139? If so, is there any schematic about this?
    Last edited by Jazzmarazz; 5th-March-2014 at 22:44.

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    Quote Originally Posted by xIceMan View Post
    Will take a photo after work. Pin 32 goes to BYTE/VPP. Was not lifted but inserted directly to the PCB.
    Yes of course, but where does it lead to? VCC or GND? This input determines whether the chip is to output in 8- or 16-bit mode.

    Quote Originally Posted by xIceMan View Post
    Here's the promised photo. Also A19 isn't touching any left over pins. I was just too lazy to remove them yet. IMG_2062.jpg
    Quote Originally Posted by xIceMan View Post
    Tried burning the ROM on a 27C322 (bent up A19 and A20) on a 1MB PCB. Connected them to B8 and B9. Same glitch. I'm now pretty sure it's the game using some protection/bank switching, since other games work fine.
    I had not heard of it until now, and there is little info on the web but I did find a photo.
    Spoiler warning:

    It is definitely unique and almost certainly contains a proprietary mapper/protection.

    Quote Originally Posted by xIceMan View Post
    Sorry for the triple/quadruple posting but I'm interested in another project and I don't want to make a new thread for every post since it all related to custom cartridges. I've seen a few games that are 8MB or larger and thus not fitting in one 27C322. Is it possible to burn such a game to 2x27C322 using a 74LS139? If so, is there any schematic about this?
    I do not know of any 8MByte games, at least not any official ones. I think that there is going to be some very special memory mapping on the original boards that support 8MByte games. you will not find a donor as far as I can tell, so you may need to get hold of a physical 8MB cart and share some photos.
    Last edited by Jazzmarazz; 5th-March-2014 at 22:53.

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    Are there any alternatives to these EPROMS? They are getting harder to source for reasonable prices (unless you guys know somewhere to obtain for cheap). I read somewhere that someone used a flash rom from a PC BIOS, but didn't list any part numbers or anything. Thanks.

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    Mouser has a 16MByte, 16-bit EPROM but it is in a TSOP package. I can't find that right now, but I will make a tutorial for using 2x 8-bit EPROMs later on.
    Any EPROM will work as long as you have the pinout correct and are sending the right bytes at the right times, to the right locations. What I mean to say is that using two 8-bit EPROMs in place of a single 16-bit EPROM can be difficult.

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    Yeah so TSOP with adapter will cost the same, if not more as the EPROM sourced from China it seems. Might not be all that worth it.

    So let me ask this - if I have a 16Mb rom and flash it to a 32Mb EPROM (cheaper, strangely) will this work?
    Last edited by brywalker; 29th-March-2014 at 21:30.

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    Quote Originally Posted by brywalker View Post
    Yeah so TSOP with adapter will cost the same, if not more as the EPROM sourced from China it seems. Might not be all that worth it.

    So let me ask this - if I have a 16Mb rom and flash it to a 32Mb EPROM (cheaper, strangely) will this work?
    Yes but you need to make sure the higher bank is not accidentally accessed instead of the part you burned to. Do this by pulling the highest address pin to ground. Alternatively, you may use this pin to switch between two 16Mb ROMs.

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    Quote Originally Posted by Jazzmarazz View Post
    Yes but you need to make sure the higher bank is not accidentally accessed instead of the part you burned to. Do this by pulling the highest address pin to ground. Alternatively, you may use this pin to switch between two 16Mb ROMs.

    Or doubling the rom so it would access the same area no matter which bank, correct?

    Thanks for the input.

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    Quote Originally Posted by brywalker View Post
    Or doubling the rom so it would access the same area no matter which bank, correct?

    Thanks for the input.
    Yep.

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    Hey guys .. hoping for some help here. Ive done nes and snes repros and making the jump to sega, running into a bit of a speed bump im sure im just missing something somewhere. the tutorial is pretty simple to follow. i have my GQ-4x with the ADP-054, and using ST m27c160-100 eproms ... Roms seem to burn fine (Read and Verify all 100%, no errors) i have a few games i want to do, but the 2 i tried were wily wars and zero wing. Wily Wars was patched (headers removed) with the s-ram fix plays fine at 60hz with the "fusion emulator" (however it does say checksum error) zero wing the same (headers removed, ntsc patched, plays it at 60hz) (also has the checksum error tho) seems all good. i found a ton of "NFL Football '94 Starring Joe Montana" carts. board has a battery and a few extra chips which i assume is s-ram? down loaded the joe rom and it says that it is 2048. so i assume the board will support 2MB. i thought i should be good to go. took my wily wars and zero wing (both in .bin format) burned with my programmer all seemed good. soldered to the board eprom going left.... and they both boot to black screens .. nothing... i tried with my sega2 with 32x attachment, just the sega 2 and a sega 3 all black screens.

    so i guess my questions are
    1. does the rom in .bin format need to not have the checksum error when tested with fusion (i didnt think so, i had no prob with translated snes's with checksum errors) however this is sega so it might be different. if so how is that fixed ?
    2. are my NFL Football '94 Starring Joe Montana boards usable with my m27c160s? does it support 2MB and have S-ram on it.
    3. do sega rom need to fill the eprom ? like zero wing is only 1MB so i just doubled it up to 2MB in my HEX editor. did i even need to do that ? i saw somewhere that you dont have to but i didnt think it would hurt.
    4. from what i understand in the tutorial if the board is 2MB and your eproms are 2MB .. there is no need for any rewiring ?

    im sure its something little im missing, and there are a few other things i was gonna test like seeing if i can burn the joe rom to the eprom and putting it back on the board and see if it works.
    any help or info would be appreciated. Thanx guys.

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    ahhhhhhh byteswap

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    Just wanted to say that Oh Mummy is working now. The problem lies within their boot code (might be a different version for the game that's being sold). Either way, using a game genie and then starting the game somewhat bypasses the BIOS and the game works. This method might work with other protected games, too.

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