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Ikrananka

Re-purpose ColecoVision Cart?

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How easy/difficult is it to re-purpose an original CV cart, replacing the original PROMs with EPROMS containing a different game/program?

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1 hour ago, Ikrananka said:

How easy/difficult is it to re-purpose an original CV cart, replacing the original PROMs with EPROMS containing a different game/program?

if socketed, very easy, if not you need to unsolder the eprom and socked a new one.

 

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But does it matter what size EPROM I put in the socket?  Does it have to match the size of the PROM removed? What about Coleco carts that contain 2 or more PROMs?

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On 8/31/2020 at 6:07 PM, Ikrananka said:

How easy/difficult is it to re-purpose an original CV cart, replacing the original PROMs with EPROMS containing a different game/program?

It's easier to order a set of boards.

https://ebay.us/ASnj1W

 

There is also one with a ZIF socket for easy testing.

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On 8/31/2020 at 7:32 PM, Ikrananka said:

But does it matter what size EPROM I put in the socket?  Does it have to match the size of the PROM removed? What about Coleco carts that contain 2 or more PROMs?

Probably not, but I haven't tested it. As long as it is the same type of eprom and has the same number of pins, you can duplicate the data, and it will probably work.

I was able to use a 27c256 in the place of a 27c64 when I was messing around with the Coleco BIOS.

 

The available cartridge boards will only support up to 32k.

 

I would suggest getting 28c256s. They are EEPROMs and work decently well.

 

The 2 PROM boards should also support larger EPROMS, but you will still have to split the ROM into the original size.

 

Another issue you could run into is the cartridge not being set up to accept 27 series EPROMS. The 3 chip Donkey Kong would be a good example of this.

 

Edited by cdoty

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Which type of PROMs are found in those cartridges? There is a significant difference in pinout between e.g. a 2364 ROM (8 kilobyte) and a 2764 EPROM, in particular the EPROM has more pins and different use of those. Computer hackers tend to build adapters consisting of two IC sockets, bending a few pins away, applying tiny wires to cross connect the desired pins in order to make it work, but it would take too much space inside a cartridge. I don't know how 16 kilobyte or larger ROM chips are wired, if those more closely match the EPROM pinouts, but you should check that before playing around. Or get replacement PCBs as suggested.

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2 hours ago, cdoty said:

It's easier to order a set of boards.

https://ebay.us/ASnj1W

 

There is also one with a ZIF socket for easy testing.

It's not for me but for someone who is helping me with a project.  I actually have a bunch of the Pixels Past boards and offered to send one his way but unfortunately where he lives it isn't reliable at the moment sending anything there.  So, he'd much rather try and re-purpose one of his existing carts.

 

2 hours ago, carlsson said:

Which type of PROMs are found in those cartridges? There is a significant difference in pinout between e.g. a 2364 ROM (8 kilobyte) and a 2764 EPROM, in particular the EPROM has more pins and different use of those. Computer hackers tend to build adapters consisting of two IC sockets, bending a few pins away, applying tiny wires to cross connect the desired pins in order to make it work, but it would take too much space inside a cartridge. I don't know how 16 kilobyte or larger ROM chips are wired, if those more closely match the EPROM pinouts, but you should check that before playing around. Or get replacement PCBs as suggested.

The eBay auction cdoty linked to above (https://ebay.us/ASnj1W) illustrates quite nicely how problematic this can be as the photos show that Smurf, in this example, has 3 PROMS and yet the total ROM size of this game is 16KB.  The PROMS are stamped with proprietary codes specific to the game rom and not the PROM type.

 

2 hours ago, cdoty said:

The 2 PROM boards should also support larger EPROMS, but you will still have to split the ROM into the original size.

 

Another issue you could run into is the cartridge not being set up to accept 27 series EPROMS. The 3 chip Donkey Kong would be a good example of this.

Agreed, the 3 PROM boards are likely to be tricky and so I had already suggested that he only try and re-purpose a game that is small in size (e.g. 8KB) in the hope that these would only have 2 PROMS.

 

The other complication is that this project requires using a completely different (1 to 2 KB) ROM in the cart.

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The ROM chips are 2x12 pins which smells 2332 (4K) or 2364 (8K) to me. A 2764 or a 27128 are both 2x14.

 

The rather uncommon TMS 2532 chip, which selected EPROM programmers can handle, is somewhat pin compatible with a 2332 ROM. Note that the more common 2732 type has the same number of pins but different pinout. There are some super rare 8K EPROM chips pin compatible with the 2364 as well but generally you don't want to go down that rabbit hole.

I suppose a 2716 (2K) might be partly pin compatible with a 2332 if you only need it to suppose small programs, but double checking would be required.

 

Too bad about your friend living in a part of the world where post service doesn't work at all or is completely corrupted. I know some locations are avoided because all mail is scanned and a lot is stolen, but it would mean almost nothing arrives to him, at least nothing that has a value above $0.50.

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6 hours ago, Ikrananka said:

It's not for me but for someone who is helping me with a project.  I actually have a bunch of the Pixels Past boards and offered to send one his way but unfortunately where he lives it isn't reliable at the moment sending anything there.  So, he'd much rather try and re-purpose one of his existing carts.

Your best bet may be a 3rd party cart that had lower sales numbers. I've seen Sord M5 and Casio PV-2000 carts that contain EPROMs.

There was probably a minimum purchase required for masked roms, which a smaller publisher wouldn't be comfortable with.

 

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7 hours ago, Ikrananka said:

The eBay auction cdoty linked to above (https://ebay.us/ASnj1W) illustrates quite nicely how problematic this can be as the photos show that Smurf, in this example, has 3 PROMS and yet the total ROM size of this game is 16KB.  The PROMS are stamped with proprietary codes specific to the game rom and not the PROM type.

The board linked removes all of the complexities of a multi rom board. You don't need 3 roms for the Smurfs to work, you only need a 16k chunk of data, which can be accomplished with a single EPROM. This applies to all roms 32k or less.

All of the wiring between chips is invisible to the Colecovision.

Edited by cdoty

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14 minutes ago, cdoty said:

The board linked removes all of the complexities of a multi rom board. You don't need 3 roms for the Smurfs to work, you only need a 16k chunk of data, which can be accomplished with a single EPROM. This applies to all roms 32k or less.

All of the wiring between chips is invisible to the Colecovision.

Yeah, that's why I use the Pixels Past boards - for the exact same reason.

 

Thanks for your help guys.  Looks like my friend is going to order some new boards from somewhere like JLCPCB.  Even with courier shipping it's very economical.  Shipping from France, via that eBay auction, to Mexico apparently is likely unreliable at this time. 

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