Pac-man Granddaughter Board

26 November, 2009 (00:05) | Arcade | By: admin

You’ve heard of a daughter board but how about a granddaughter board?

I built this thing a couple of years ago. I’ve been working with a fellow collector on some hardware development and he wanted to see an example of a logic IC hiding under and EPROM so I figured I might as well write something about this board.

The picture below shows 2 boards. One is a Ms. Pac-man daughter board and the other is my home brew Pac-Man board tester. It’s a daughter board on a daughter board so I like to call it a granddaughter board.

I purchased these boards from a fellow collector a while back. They’re intended to be used with Galaxian and replace all of the game ROM code on the board with a single EPROM. The daughter board is intended plug into the CPU socket and works quite well for Galaxian. Fortunately the ROM code for Pac-Man and Galaxian share the same address space (Pac-Man just has more ROM) so the board can be used for Pac-Man as well. At least up to the limit of the Galaxian address space. I’m not sure that it would work for the complete Pac-Man code but it runs the test ROM nicely.

Here are a couple of pictures showing the GAL (programmable logic) installed on the board. You can see where the EPROM will be mounted over the GAL.

The problem with using this board on Pac-Man boards is that the sync bus controller board covers the CPU socket. I modified a Ms. Pac-Man daughter board to basically act as a remote mounted 40 pin socket. You plug the ribbon cable into the CPU socket and the socket on the daughter board is then connected in parallel with the one on the other end of the cable. This board will now work to remote mount any 40 pin socket. It’s not limited to Z80.

This picture shows the original Ms. Pac-Man daughter board. I removed all of the chips. Fortunately all of the chips are socketed so it’s easy to remove them all.

I had to cut one trace and install one jumper to make it work but it wasn’t difficult to figure out.

Here we see the board installed on the daughter board.

These pictures show the GAL hiding under the EPROM.

Here’s the board installed on the daughter board.

As you can see I have more than a few Pac-Man boards to test and sell. Hopefully the development project I’m working on right now will motivate me to get working on these things. More to come…