Friday, May 15, 2020

Decapping is pure fun, fear and adrenaline

I decapped my last 8751H over 6 month's ago. So i was pretty excited when f250v contacted me for decapping a protected 8751H from his Street Figher (bootleg).
Read more about here.

He shipped the mcu last monday, i received it today and as i had a short period of free time i immediately started to work on it.

To be true, decapping a chip is pure adrenaline, a little bit of fear and in the end alot of fun. While it proved another time that my decapping method is working pretty good, it's always risky to decap a chip. (don't use too much heat / did i use enough polish / hopefully i did not accidentally cut a wire /...)

In the end it took about 15 minutes to open the chip, 5 minutes to erase the lock bit and after another 5 minutes we had the dump.

The next interesting fact was, that this dump matched the other existing Street Fighter mcu dump, which was just added 8 days ago to MAME (here). The previous dump was only possible, because an unsecured 8751H was found. 

Anyway, this confirmed the existing dump!

Thx to f205v for sending the 8751H to me, it was nice variety to my currently other work.


  1. I didn't know how to contact Citylan but I wanted to say him I dumped this mcu some days ago and sent it to mameteam. I wanted to try to decap it but no need because mine was unprotected. Mame team said my dump is working fine ; maybe it's a different one N

  2. Edit : if I had read the totality I should have read that the dump you mention is the one I provided to Mame Team...

    1. Correct!
      Your dump was added to mame about 10 days ago. It's definitely good to have a confirmation of the mcu-dump. So the decapping was not completely worthless. It was at least also good practice for me again. ;-)

    2. Yes you are right, the decapping was absolutly not worthless ; it could have been a different version. Now we know that a good dump is done so I can consider to try decaping this chip one day just for fun, fear and adrenaline :)

  3. So can these Decapped chips be re-used in the original PCB or replaced with an un-protected one to preserve the physical hardware??

  4. Both ways are possible!
    If everything goes well, the decapped chip can get reused on the original board and will work perfectly!
    On the other side, you can take the decapped rom-dump and burn it on a new/empty 8751H or even better you can burn it on an AT89C51 (which are cheaper these days) and use those on the real boards.