Read ROMs without desoldering them?

massimiliano · Apr 19, 2017

Hi, I was wondering about this, just in case I may need to compare CRCs for some reason...

Now, would it be possible to use a piggyback socket to connect an eprom programmer to a rom mounted on a (turned off) pcb? (upper side...like biosmasta on a 68k)

I have't tried yet but I was wondering if I'm missing something obvious?

Thanks!

donluca · Apr 19, 2017

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.

pulstar · Apr 19, 2017

A lot of times EPROMS/MaskROMs are tied together and switched on via logic on the PCB. I would assume this would conflict with getting a decent read when it's in circuit, might be wrong though.

massimiliano · Apr 19, 2017

thanks, I thought there would have been some catch like that.. I remember Jeff building something to dump the Power Spikes II early release, so there has to be some issue just "face hugging" the rom...

I'd like to end with some sort of standardized approach/kit, so everyone could easily troubleshoot carts!

aha2940 · Apr 19, 2017

AFAIK, all the data lines, ground and 5V lines are shared between all the same-purpose chips (all the C, V or P chips). The only lines that are controlled are chip-enabled and output-enabled, which makes it that only the chip that gets those signals is read (that's how the neogeo does it too). A device as described by massi seems possible, but it may require a lot of hand-soldering.

Regards.

massimiliano · Apr 19, 2017

Thanks....do you think it may be worth to design two boards with sockets to couple the MVS/AES layout (maybe jumpers to activate which rom you need to read on need basis)

...forst question...is it safe to say the MVS boards are reasonably sharing the same layout? (going to check cart pics now)

Edit:

never mind...a modular design may be required, given too many different layouts..

kuze · Apr 19, 2017

IMO the best way to do this would be to use something like the NeoSD (or Darksoft cart) and write a homebrew app that will dump a game in another slot of a multi-slot system to SD card.

Alternatively you could design a PCB that would read a cart similar to how the NeoGeo does (via the cart edges) but that sort of seems like re-inventing the wheel when the NeoGeo could potentially handle a lot of it for you.

aha2940 · Apr 19, 2017

kuze said:
IMO the best way to do this would be to use something like the NeoSD (or Darksoft cart) and write a homebrew app that will dump a game in another slot of a multi-slot system to SD card.

This sounds interesting, however I am not sure you can access the neosd slot and the slot with the dumpable game at the same time, but I think Raz/JMKurtz/neodev/neosd can tell us more about that.

kuze said:
Alternatively you could design a PCB that would read a cart similar to how the NeoGeo does (via the cart edges) but that sort of seems like re-inventing the wheel when the NeoGeo could potentially handle a lot of it for you.

I think Raz said somewhere that only P chips could be read directly in sequence, that's why the unibios can only test the P rom, not every rom on a cart.

GadgetUK · Apr 19, 2017

aha2940 said:
This sounds interesting, however I am not sure you can access the neosd slot and the slot with the dumpable game at the same time, but I think Raz/JMKurtz/neodev/neosd can tell us more about that.

I think Raz said somewhere that only P chips could be read directly in sequence, that's why the unibios can only test the P rom, not every rom on a cart.

Yes, that's correct! The CPU only has access to the P ROMs. But it's totally possible to read an EPROM that way, the hardest part is finding something that will grip the chip in order that you can read it. To my knowledge there's nothing out there that can fit over the profile of a DIP chip and grip the pins? I guess you would need to make some kind of slip over adapter.

Xian Xi · Apr 19, 2017

GadgetUK said:
Yes, that's correct! The CPU only has access to the P ROMs. But it's totally possible to read an EPROM that way, the hardest part is finding something that will grip the chip in order that you can read it. To my knowledge there's nothing out there that can fit over the profile of a DIP chip and grip the pins? I guess you would need to make some kind of slip over adapter.

Single wipe style socket can.

kuze · Apr 19, 2017

aha2940 said:
I think Raz said somewhere that only P chips could be read directly in sequence, that's why the unibios can only test the P rom, not every rom on a cart.

Ah right on, that could definitely be a hurdle to that sort of approach.

skate323k137 · Apr 19, 2017

Neo Geo roms are pretty easy to remove, the holes aren't through plated. With a good desoldering tool you can take a rom off in a few minutes.

massimiliano · Apr 19, 2017

skate323k137 said:
Neo Geo roms are pretty easy to remove, the holes aren't through plated. With a good desoldering tool you can take a rom off in a few minutes.

Thanks, but the whole topic is about avoiding that.

skate323k137 · Apr 19, 2017

I get that. but you are probably going to end up doing a lot more work to read them in-line. If they were small SMD chips or something I could see going through the trouble, but not on a neo board. I hope you find a good solution.

aha2940 · Apr 19, 2017

skate323k137 said:
Neo Geo roms are pretty easy to remove, the holes aren't through plated. With a good desoldering tool you can take a rom off in a few minutes.

Have you ever tried to desolder a chip from a Magician Lord, Cyber-Lip or NAM cart? earlier carts have solder on both sides, those are a pain to desolder, and some of those carts are expensive (read: worth troubleshooting and repairing) so massi's approach still makes sense.

massimiliano · Apr 19, 2017

I think so far it seems worth at least discussing it, if it all comes to make an adaptor, I think we could come with a solution.

My question I guess is basically, has anyone ever tried wiring the rom while still in the board and see if it can be read?

massimiliano · Apr 19, 2017

kuze said:
IMO the best way to do this would be to use something like the NeoSD (or Darksoft cart) and write a homebrew app that will dump a game in another slot of a multi-slot system to SD card.

Alternatively you could design a PCB that would read a cart similar to how the NeoGeo does (via the cart edges) but that sort of seems like re-inventing the wheel when the NeoGeo could potentially handle a lot of it for you.

Nice, really elegant...all I can tell is that the bios can display all the titles available in the 4 slots, when configuring the soft dips...how that data is fetched may clear some questions.

Edit:

not sure if MVS and AES carts may differ enough to make things simpler in the MVS case above?

HeavyMachineGoob · Apr 19, 2017

aha2940 said:
Have you ever tried to desolder a chip from a Magician Lord, Cyber-Lip or NAM cart? earlier carts have solder on both sides, those are a pain to desolder, and some of those carts are expensive (read: worth troubleshooting and repairing) so massi's approach still makes sense.

Early carts like you said, along with SNK's late copy-protected releases (KOF 99 onward) have thick double sided boards and are indeed hard to desolder. The early boards are a few difficulty notches below the likes of PROGLBA and CHAFIO though. Those are ridiculously tough boards to desolder.

skate323k137 · Apr 19, 2017

I've been lucky then. Don't get me wrong I'd love to see a good solution for this.

aha2940 · Apr 19, 2017

HeavyMachineGun said:
Early carts like you said, along with SNK's late copy-protected releases (KOF 99 onward) have thick double sided boards and are indeed hard to desolder. The early boards are a few difficulty notches below the likes of PROGLBA and CHAFIO though. Those are ridiculously tough boards to desolder.

I have never tried anything on such boards, because when they break, it's usually the custom/altera chip, so they break for good.

skate323k137 said:
I've been lucky then. Don't get me wrong I'd love to see a good solution for this.

No worries man, just pointing out that not all neogeo boards have easily removable chips, therefore a solution like this would definitely be useful.

xsq · Apr 20, 2017

massimiliano said:
thanks, I thought there would have been some catch like that.. I remember Jeff building something to dump the Power Spikes II early release, so there has to be some issue just "face hugging" the rom...

Yeah, that's what I thought of reading this thread as well... maybe getting in contact with Jeff would be the next logical step, seems he did some work on this already - and he knows this stuff...

btw. I think this is a great idea.

massimiliano · Apr 20, 2017

PM'd him, hopefully all his effort to get a SuperVolley 94 dump won;t get wasted!

Pedrobear · Apr 20, 2017

Yeah, only P data can be read from the system.

You need a device that piggybacks on the chips or brew some cart reader for what you are looking for.

What's the goal tho? Singling out a single faulty chip is usually easy with available dumps out there.

massimiliano · Apr 20, 2017

I think ruling out a ROM is faulty by comparing CRCs without desoldering it would be faster and safer, with less stress on the ROMs.

My guess was that just a piggyback socket would have worked, if so, I guess people would be interested in getting such tool manufactured.

...still not sure what the issue with such approach may be, I can try but not now as I'm about to move.

Edit:

to avoid something like this i.e. (maybe not the most correct case, but you got the idea):

http://www.neo-geo.com/forums/showt...lash)-Reflow&p=4192123&viewfull=1#post4192123

OR

http://www.neo-geo.com/forums/showthread.php?270828-Galaxy-Fight-sound-issues&p=4192489#post4192489

Pedrobear · Apr 20, 2017

What I meant is by observing visual/sound defects and looking into the rom data, you can determine which chip is bad. Without touching anything but files on your computer.

Are you trying to fix something or is it just hypothetical question?

Read ROMs without desoldering them?

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