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Game Gear Rom Swaps - Codemasters
Post Posted: Mon Mar 18, 2019 11:47 am
Hi,

Long time lurker first time poster, I'm messing about with swapping ROMs because I want to play about making repros for Game Gear games.

I've successfully turned a bootleg cart into a copy of Frogger, it used an off the shelf 27c4000 eeprom with a separate mapper so was easy to reprogram.

As all Codemasters games also use a separate mapper I figured I could make my own Dinobasher (256k) by swapping off the mask rom for an e/eprom.

I'm a little stuck as to a suitable chip to use. This is the board:



it uses a 32 pin mask ROM, probably something like a 23C1010 which its pinout matches exactly. It uses an 18bit address A14, A15 and A16 all go to the mapper so assume this is how to mapping is controlled.

I can't find a suitable chip in the 27c family with 18bit addresses or 32 pins. 27c512 is 28 pins 17 bit address and 27C1024 is 40 pins.

This is not my area of expertise so I'm kind of puzzling through and working it out by trying stuff.

Any advise on what chip to use? ideally a soic/tsop for space reasons, I could do a little re-routing but i assume i need all 18 address bits for the mapping to work.

Thanks,
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BC4FF98A-8F53-43EF-839A-92BE71721331.jpeg

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Post Posted: Mon Mar 18, 2019 11:58 am
I'm thinking I over thought it, my original bootleg used a 27c4000, turns our that would probably work in this instance too or a 27c1000, just need a SOP version of it.
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Post Posted: Wed Mar 20, 2019 5:41 am
FYI: I'm not against the making of repros per se, but I am very against the buying and selling of them. As the translator and script dumper of a number of completed GG translation projects including Madou Monogatari, Rayearth, Sailor Moon S, Crayon Shin-chan, and others I want to be clear that combining my work (translation patch) with the original work (ROM) and distributing it is against my wishes and against the spirit in which fan translators distribute their work. Fan translators go out of their way to distribute patches, not ROMs, and never sell their work. It's not asking much to expect those who didn't even work on the translations to live up to the same standard. I have no idea what your intentions are, but I want to make mine known if you're going to "play about making repros" as you say.
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Post Posted: Wed Mar 20, 2019 6:07 am
I respect your opinion but your making way too many assumptions about my intentions and frankly I find it insulting.

The two games I mentioned are both unreleased, are not fan translations, have nothing to do with that community and are just for my personal pleasure in producing my own carts and labels for my GG collection.

But honestly I don’t see why I have to justify my intentions to you at all.

The internal mapper chip in GG roms has long made repros on this platform unviable. If that problem was solved tomorrow and someone started mass producing GG repro carts I would expect them to be stuck with stock for a long long time as the market just isn’t there.

For example no one is getting rich on making repro carts for the SMS. There are obviously scammers making them for the NES but that market is crazy anyway.

I think your fears that someone will take your work build a cart and sell it are pretty unfounded because even if It did happen it would be so small scale.
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Post Posted: Wed Mar 20, 2019 9:07 pm
Isn't the GG's unusual pin connector also unviable for reproduction, or was it the cart slot that is trouble to repro (I think things like Retrode want the user to supply a donor port?).
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Post Posted: Wed Mar 20, 2019 10:41 pm
It's the cart slot that is hard - card edges are relatively easy as you just lay out the circuit board at the right size and leave off the insulating layer, plus try to get the right thickness.
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Post Posted: Thu Mar 21, 2019 11:23 am
The frustrating thing is that the Hong Kong knock off merchants had all these problems solved in the 90's

If only I could find that wizened old Chinese guy with the gerber files for his bootleg boards and whatever ICs they used for the mapper it would solve everything.
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Post Posted: Thu Mar 21, 2019 7:48 pm
kejoxen wrote
I respect your opinion but your making way too many assumptions about my intentions and frankly I find it insulting.

The two games I mentioned are both unreleased, are not fan translations, have nothing to do with that community and are just for my personal pleasure in producing my own carts and labels for my GG collection.

But honestly I don’t see why I have to justify my intentions to you at all.

The internal mapper chip in GG roms has long made repros on this platform unviable. If that problem was solved tomorrow and someone started mass producing GG repro carts I would expect them to be stuck with stock for a long long time as the market just isn’t there.

For example no one is getting rich on making repro carts for the SMS. There are obviously scammers making them for the NES but that market is crazy anyway.

I think your fears that someone will take your work build a cart and sell it are pretty unfounded because even if It did happen it would be so small scale.


No one likes having their intentions questioned, but if you find my questioning of your intentions insulting, I assume you'll understand how insulting I find the selling of a games' rights holder's IP along with the translations I've worked on for free. Posts like these raise a huge red flag, and I have to work on the assumption that some folks just haven't bothered to think about the morality of their actions in regards to buying or selling "repro" carts, or to consider it from the perspective of those actually working to translate games without compensation.

I've had several productive conversations with others who have told me that they've decided not to promote or purchase repros after thinking about what I've said. What other way is there for folks to understand they are participating in something that fan translators, justifiably, find unpleasant than for those fan translators to make their wishes known? I'm not truly a rights-holder and cannot issue a C&D to repro makers, but I can let folks know that they are not made with my consent, and why it stands to hurt the fan translation community on multiple levels. It's up to those buying and selling them to make up their own minds after considering what I've said. If nothing else, I'm not going to let them get away with a clear conscience.

You've stated that you're making these for yourself, and not even using fan translation patches, so that's that. I was also not aware that GG repros are difficult technically, I've mostly seen repros of SFC/SNES and Famisom/NES games I've worked on being sold. I'm happy to hear it and you'll find no argument from me. Good luck.
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Post Posted: Sat Mar 23, 2019 8:35 am
Thanks for taking my development help request way off topic.

Anyway,

I have a copy of micromachines as a donor, I've confirmed that the mask rom used as 27c4000 compatible in a sop package. The pinout matches as far as i can tell.

I de soldered the old mask rom from the board and dropped it in my TL866 programmer. If i select a 27c4000 and read the ROM I get data, but its garbage.

This makes me think that if i burnt a 27c4000 and dropped i on the board it wouldn't work, I need to format the data somehow or understand why the data i get back from the mask rom is unusable.

I know there is a lot of information on the forum but its so spread out and what seems to often happen is someone asks a question then gets a solution then never reports back if it worked or not. Also i cant find anything specific about dumping CM games.

So if anyone can give me an idea of what i need to do to get usuable data off of my micromachines rom chip so i have a good idea of what i need to do to my dinobasher data to put it on a rom the GG can read that would be fantastic.
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Post Posted: Sat Mar 23, 2019 3:58 pm
Quote
I have a copy of micromachines as a donor, I've confirmed that the mask rom used as 27c4000 compatible in a sop package. The pinout matches as far as i can tell.

I de soldered the old mask rom from the board and dropped it in my TL866 programmer. If i select a 27c4000 and read the ROM I get data, but its garbage.


Those two things looks like they are maybe contradicting each others. Maybe it isn’t 27c4000 compatible?

If the data you get doesn’t show repetitive pattern, you could probably analyze extracts of it and compare them with the known dump to help understand the issue.

Some EPROM used on GG dev boards have two swapped out pins, maybe there is a swap of this kind here. I haven’t tried dumping or replacing a CM game straight out of the ROM chip so i don’t know.


(I also personally think donor-based homebrew carts are silly, wasting perfectly fine (and somehow uncommon) cm games or asian bootlegs, and above all it will eventually tempt all kind of less consciencous people to do the same thing. I would advise just playing them in a GG everdrive or another flash cart.)
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Post Posted: Sat Mar 23, 2019 9:33 pm
Well that’s that idea in the bin then.

On to something else.
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Post Posted: Mon Mar 25, 2019 8:55 am
This is really a great initiative that you are taking up.
Just curious are you an electronic engineer?
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Post Posted: Mon Mar 25, 2019 11:31 am
For Game Gear cartmodding I personally use 27c040 eprom (SOP32 from Atmel) and cheap 1Mb game as donor.
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Post Posted: Mon Mar 25, 2019 11:58 am
That’s cool,

Can you share some photos and examples of 1mb games to use a donors?

The 27c040 and 27c4000 are pin compatible.
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Post Posted: Mon Mar 25, 2019 12:50 pm
I made a video a while ago about my catmodding of R-Type for Game Gear: (video in french but english subtitles available).
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Post Posted: Mon Mar 25, 2019 2:57 pm
Shame to use Garfield, as R-Type is a 512k rom maybe you only need to find a 512 cart with a mapper, hopefully a crappy sports game.

I’m going to just try slotting a 27c4000 onto my CodeMasters board and see what happens.
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Post Posted: Mon Mar 25, 2019 4:19 pm
Right forget all of this,

just found a dude who started making these repro boards for $7.50

https://www.mortoffgames.com/index.php?route=product/product&product_id=958&...

I've ordered three to test out.
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Post Posted: Fri Apr 12, 2019 4:58 pm
Just to update on this i was over thinking it,

a 27c040 or 27c4000 works fine for the Codemasters board you can burn a CM game and just swap them in.
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Post Posted: Tue Apr 16, 2019 4:46 am
My first batch of personal repros. I suppose repro isn’t correct as some of these never existed of the GG.

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