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  • Joined: 23 Jun 2019
  • Posts: 2
  • Location: London
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EPROM Help!
Post Posted: Sun Jun 23, 2019 11:11 pm
Hello, I am new to this site. I would like to have a go at programming an EPROM with a sms Alex Kidd game I made using Kiddex, and soldering into an old cart I have. I also want to complete my Sega Master System game collection by creating carts of games I’ll never be able to find or afford (Smurfs etc...) I have read many tutorials,forums and watched videos but still have a few questions I need help with:

1) Can anyone recommend an eprom programmer (preferably I can use with a Mac), I’ve been looking on eBay and Amazon but not sure which one will do the job.
2) Can the EPROM chips taken from old master system carts be erased using an UV eraser? And then re-programmed?
3) I understand from reading various tutorials that there are different EPROMs available, eg: 512kb, 256kb, 128kb, is there a list of what EPROMs to use with what games.

I am very new to this and would welcome any advice.
I thank anyone that can help me with this endeavour!

(Ps in the 1980’s I owned a Master System 1, light gun, 3D glasses, all boxed, about 80 games which I looked after and were all in mint condition.... I traded it all for an Amiga, that turned out to be broken. Guy in the shop wouldn’t trade it back as I didn’t have a receipt.... it was the next day! I was about 14 and have always regretted it.) so last year I decided to begin a new SMS odyssey and collect as much as I could. This website, the people that run it and the contributing users have been invaluable to my research and collecting... THANK YOU SO MUCH!

DREW (a 14 year old stuck inside the body of a 40 something year old)
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  • Joined: 08 Sep 2018
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Post Posted: Sun Jun 23, 2019 11:35 pm
OK so to cover everything. Any official cart ever released by SEGA all use MROM or Mask ROMs. These ROMs are hardware programmed from factory and can never be erased.
As far as chips go using an official SEGA mapper IC you cannot use a chip larger than 4 megabit. Speaking of the SEGA mmc, for any game larger than 64k you need a memory mapper chip. Most of SEGA's Mask ROM chips incorporate the MMC within them making it nearly impossible to make clones using an old SEGA cart board.
You can however buy boards with a chip pre installed on them that emulate the SEGA mmc.
As far as chip size, try and get a chip that matches the size of the ROM file. Be mindful to do any conversions from bits to bytes and vis versa so you pick the appropriate chip (ie 512KBytes is 4Mbits).
For a programmer, hopefully someone can follow up on that as i am not aware of which to pick for use with EPROMs since often I use Flash EEPROMs for my projects.
Good luck!
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  • Joined: 23 Jun 2019
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  • Location: London
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Post Posted: Mon Jun 24, 2019 7:09 pm
Thank you for this info, very helpful. So would this be the correct order of events from beginning to having a cartridge with a new game on:

1) Take an old cartridge, open it up and unsolder the back of the 28 pins of the chip.
2) Take a blank EPROM chip and put it in the EPROM programmer (I still need someone to recommend an EPROM programmer to buy)
3) Using EPROM programmer software, ‘burn’ a new ROM onto the chip (taking in into account chip size and ROM size as per your instructions). Run a test through an emulator to make sure chip/Rom are working.
4) Once new chip has new ROM on it, replace it in the cart PCB and solder it back in.
5) Put cart back together and play game!

Can anyone see any glaring mistakes or anything I’m missing, as you can see I’m a complete noob but I am a quick learner.

Thank you
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  • Joined: 08 Sep 2018
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Post Posted: Mon Jun 24, 2019 11:35 pm
You're still missing an MMC or memory mapper chip. The 28pin chip package mask ROM that comes on an original SEGA has the MMC built directly into it. Without an MMC you can only program a max size of 48KB games onto a replacement ROM chip even if that ROM chip package has the same pin count and can store more than 48KB of data.
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  • Joined: 05 Nov 2014
  • Posts: 229
  • Location: Auckland - NZ
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Post Posted: Tue Jun 25, 2019 4:22 am
After burner or Space gun both have a separate mapper and rom chips on their boards. These both make good doner carts for making your own games and are usually easy to find. If you want battery backed up memory as well (a few games use it for game save) see if you can find a cheap copy of penguin land to use as a doner.

As for a programmer.. i use a cheap tl866a usb programmer. It seems to do the job and i havnt had any issues with it. It may not do aome of the bigher 16bit eproms very well but you wont need to worey about thay for master system games. Don't think they have mac software for it tho.
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  • Joined: 24 Sep 2013
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Post Posted: Tue Jun 25, 2019 3:06 pm
Drew74 wrote


1) Can anyone recommend an eprom programmer (preferably I can use with a Mac), I’ve been looking on eBay and Amazon but not sure which one will do the job.


If you don't fear using a command line tool (on Mac) or can use a Windows machine (GUI) the TL866 and clones work very well for FLASH/EEPROM programing (I'm using that one).

The official tool is windows only but there are tools that work well for Linux/Mac, command line only AFAIK.

Regarding the mapper chip, it can be recreated using discrete components but it would require doing a cartridge board for that mapper clone on purpose.
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