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Thread: Read ROMs without desoldering them?

  1. #26
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    Quote Originally Posted by Pedrobear View Post
    What I meant is by observing visual/sound defects and looking into the rom data, you can determine which chip is bad.

    Are you trying to fix something or is it just hypothetical question?
    I'm not trying to fix anything yet, I'm investigating feasibility for a (I think/hope quite simple) tool that would make things easier, and comparing CRCs seems significative information.

    What do you mean by looking into ROM data? I mean, without desoldering.
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  2. #27
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    Say, you have a faulty art of fighting 2 cart. Backgrounds are bad, characters mostly ok.

    Work out the C rom data, turning it into something you can look at: http://nsa37.casimages.com/img/2017/...8001118635.png (warning HUGE pic)

    By looking at the data, you can observe backgrounds are stored first, so you know you have an issue with C1 and/or C2. Adding a little more expertise (I don't have the odd/even pixels distribution off my head right now) you would be able to single out C1 or C2.

  3. #28
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    Quote Originally Posted by Pedrobear View Post
    Say, you have a faulty art of fighting 2 cart. Backgrounds are bad, characters mostly ok.

    Work out the C rom data, turning it into something you can look at: http://nsa37.casimages.com/img/2017/...8001118635.png (warning HUGE pic)

    By looking at the data, you can observe backgrounds are stored first, so you know you have an issue with C1 and/or C2. Adding a little more expertise (I don't have the odd/even pixels distribution off my head right now) you would be able to single out C1 or C2.
    Ok, I understand what you mean.

    Don't take me wrong, sound great but I still see useful a tool to dump the ROMs without desoldering, instead of trying to infer that way, which as you just explained requires certain expertise not everyone may have.

    Think of it as a (standardized?) way to quickly fix faulty ROMS or enable an end-user to provide reliable data to others helping him.
    Last edited by massimiliano; 04-20-2017 at 02:00 PM. Reason: typos
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  4. #29
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    Options are always good.

    I think the average joe is more likely to post pics of issue and ask dev guys about it that build a dumping device tho

  5. #30
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    Quote Originally Posted by Pedrobear View Post
    Options are always good.

    I think the average joe is more likely to post pics of issue and ask dev guys about it that build a dumping device tho
    Yeah..that's the point, I hope we may consider a small batch production so it could be available for everyone...something to keep as part of the swiss army knife, along with diagnostic roms, unibios and other useful things.
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  6. #31
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    Singling out the bad C ROM is always a bit of a pain in the ass. If you're lucky, the failure is detectable at hardware level using a logic probe. Sadly, I've had ROM chips fail internally, in a way that's really only detectable when you try to read data off it. Dumping a ROM and examining the file in a hex editor is the most reliable method.

  7. #32
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    Total solderless solution is cart edge only tho.

    Arduino mega hooked to cart edge could propably do the job.

  8. #33
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    that sounds cool! but would it involve some chip on the board to access the roms? in that case not sure about troubleshooting...but still a very cool dumper!

    OR

    if all roms are connected as we fear, we need some logic to "deplex" the reads? would that be possible to implement such reader via arduino, plugging via piggyback?
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  9. #34
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    Hmm, thinking of piggyback, you would need to do a lot on pin lifting to be able to apply an address without applying voltage to some chip output.like, lift the whole neo-273 to read C chips for example.

  10. #35
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    Please cope with me as this is not my cup of tea...would the "garbled" data read from the rom (still connected to other elements) rearrangeable by i.e. an inline arduino with logic?
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  11. #36
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    it won't be garbled if you disable other chips on the bus. More pin lifting here.

  12. #37
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    the requirement is to do not modify the cart.
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  13. #38
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    Then you can only do it from the cart edge, which would require operating the cartridge logic so the data is "unloaded" properly.

    You can't have your cake and eat it too. If you want to read the ROM chips directly, pin lifting is involved.

  14. #39
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    Ok got it, I thougt the edge solution would allow only P rom dump?

    If instead the logic can be arbitrary and access each ROM separately, it still would be cool *but* the whole cart (rom and other chips) has to work, which may not be the case...

    Anyway, sounds useful to dump a prototype (which may be the solution Jeff built? btw, no sign of him :/ )
    or rule out the roms...makes sense to me.

    thanks everybody, it would be great if we (you) could come with the logic to implement in an arduino!
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  15. #40
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    I think the "P ROM dump only" was stated if using an MVS to do the dumping, even if you were to use something like a NeoSD. The BIOS only has direct access to the 68000 ROM bus (P ROM).

    Now if you had something like a Retrode dumper, an adapter that could decode the ROM addressing on each of the Neo Geo's 6 ROM buses, then there wouldn't be any problems. Well, the one exception would be encrypted ROMs like with late releases. Thing is, the original cartridges already have the decryption logic, it's just a matter of telling to cartridge logic to hand over the ROM data.

    I don't have an Arduino. Building an AES/MVS adapter wouldn't be much harder than the Retrode. Heck, NG Dev Team has a custom made flash writer which is like a Retrode in reverse, designed to flash their custom Neo Geo boards.

  16. #41
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    OK, gotcha....awesome.

    Dumb question but, MVS vs AES, IIRC the AES cart has more chips, which would be present in a MVS motherboard, correct?

    Sounds like dumping MVS carts may be easier?

    I can put together both cart connectors and an Arduino...either ship them to someone or start wiring them here...anyone onboard?
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  17. #42
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    The only real difference between MVS and AES is the location of the C ROM demultiplexing logic and the cartridge slot size. It goes by a few different names, PRO-CT0, NEO-ZMC2, NEO-CMC* etc. The sprite data (C ROMs) in an AES cart is already "unpacked" at the cart edge, unlike the MVS where the sprite data still needs to be demuxed before use. It really only adds or removes a step depending on how you look at it.

    *Technically the NEO-CMC on the CHAFIO board can act as a NEO-ZMC2 and not, it's a custom chip used on both MVS and AES CHAFIO boards
    Last edited by HeavyMachineGun; 04-21-2017 at 04:57 PM.

  18. #43
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    ok so would basically a software difference we could switch with a jumper MVS/AES?

    I see why Pedrobear mentioned the Mega, would that suffice all the edge pins? (guess not all are used?)

    Edit:

    Any tech/dev documentation on the subject by chance? :/
    Last edited by massimiliano; 04-21-2017 at 06:16 PM.
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  19. #44
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    You'd need a breakout board for both cart formats, giving pin headers for each contact to hook up to.

    I don't think Arduino mega would have enough pins to do everything at once, you'd have to make multiple set ups / pinouts.


    Buses are documented on the wiki.

  20. #45
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    Quote Originally Posted by donluca View Post
    Interested in this as well. I always wanted to dump the content of my 138-in-1 chips to replace the clones/hacks with missing games, but don't want to desolder and solder them again.
    Were these collections even dumped? I've read about a couple of people expressing interest in doing it, but I guess they ultimately gave up because desoldering and dumping all of those surface mounted roms would be such a pain. On the other hand, before NeoSD, that would have been the best shortcut to take. Replace the hacks with missing games, and you get yourself an all-in-one.

    I'm really curious if it's even possible to hack those carts into full, working NG collections.

  21. #46
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    Quote Originally Posted by Morden View Post
    Were these collections even dumped? I've read about a couple of people expressing interest in doing it, but I guess they ultimately gave up because desoldering and dumping all of those surface mounted roms would be such a pain. On the other hand, before NeoSD, that would have been the best shortcut to take. Replace the hacks with missing games, and you get yourself an all-in-one.

    I'm really curious if it's even possible to hack those carts into full, working NG collections.
    I don't think so, but I gotta admit I didn't look too much around.

    Also, I don't see any issues in replacing the hacks with legit games as long as the hack is bigger than the game, so you can replace it and pad it to the hack's size.

    Again, I might be missing something along the way but yeah, I don't see myself or anyone else for that matter taking out each SMD chip and dumping them.

  22. #47
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    Pedrobear is correct - you'll run into issues trying to read an eprom in-circuit.

    We dumped Super Volley 94's P1 using the PC2NEO (USB) device from Razoola. I plan on building an adapter to go after the M1 & S1 when I get some free time - just haven't had the chance to do it. I'll probably try this with a Pi board since that's what I have handy to make it generic enough for anyone to use. If someone has a chance to build one sooner than me, let me borrow your adapter so that we can finish off SV94!

  23. #48
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    That's great Jeff! This seems a bit out of my league, but if you need contributors, count on me!
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