82S123 bi-polar PROM replacement kit (82S123-to-27512)

What is it

The 82S123-to-27512 is a universal replacement solution to replace a 82S123 bi-polar PROMS with newer easy to find fast EEPROMs. This kit is a very small adapter board that can take a cheap and easy to find W27C512 EEPROM and replace 82S123 bi-polar PROMS.


I created this kit as I work on a lot of early 80s arcade games, every once in a while I need to replace a 82S123 bi-polar PROM. These bi-polar PROMS were made in the 70s and VERY hard to find, and VERY expensive and the most of normal in-expensive programmers will not even program them. Whenever I needed one I needed to use a outside source and it was expensive to get.

I designed this adapter to solve the problem and allow me to replace 82S123 or with FAST electrically erasable EEPROMS. I personally use a W27C512 45 ns EEPROM.

What's included and what does it look like

The 82S123-to-27512 is the UN-ASSEMBLED parts to make the adapter board as shown in the image

You will receive the parts to make 4 adapter boards, which include:

  • 4 x adapter PCB boards
  • 4 x 28 pin solder tab sockets
  • 8 x 8 pin header strips

If you choose the "EEPROMS included" finish option, you will receive 4 W27C512-45 EEPROMS along with the adapters.

How does it work

It's very easy, follow these steps in ORDER:
  1. Solder together the header pins into the board.
  2. Solder the socket into the new board
  3. Program the replacement EEPROM in an EEPROM programmer (such as the GQ-4X), and program the ROM image to want to replace. There is NO need to "double, triple, or quadruple" the image on the new chip, simply burn the image AS is.
  4. Insert the programmed EEPROM into the socket
  5. Insert adapter into game board ROM socket!
  6. Play!


  • Most uses of these 82S* series PROMs must have VERY fast access times you CANNOT use normal EPROMS with access times in the hundreds of milliseconds to replace these. The EPROMS included with the EEPROM options the (Winbond 27C512-45) are VERY fast and have worked in my limited tests (galaga, millipede, sega/gremlin VIC boards to date). However I CANNOT guarantee they will work for your specific use.


Approx dimensions when assembled:
1 1/2" wide
15/16" wide
3/4" tall (including height of a WC27512 inserted into the socket, including length of adapter legs)


These can also be used to read data off of existing 82S123. Instead of installing 2 x 8 pin terminal strips, instead install a 16 pin socket. Instead of installing a 28 pin socket, install 2 x 12 pin headers. Then insert the original 82S123 in the socket. Read the chip in a EPROM programmer as a 27512.

Important note:
When reading as a 27512 you will have 65536 bytes data file.
Use the online converter to convert the image to a normal 82S123 image file.

How do I buy them?

Buy them on

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