4 Chip 512k Upgrade

The Problem

Back in 2003 I was trying to figure out why one of my 16 chip memory board had stopped working for some reason.  I actually solved my problem by wiring up a couple of 256k SIM modules using a schematic I found on the internet.  That got me thinking about trying to create a whole new solution for memory upgrades for the CoCo 3.

Over the years I have collected many old ISA cards, always thinking about ways to wire them up for use on the CoCo.  This time around I found it easier just to take the memory chips of some of the 512k -1MB boards and using them for a 512 memory upgrade project.

The Solution

I needed a reason to design my own board and have a couple of them made.  This sounded like the perfect 'project'.  Checking my latest edition of Circuit Cellar I found several programs available for use in creating circuit boards.  A program from Cadsoft called Eagle seemed like a good fit for this small project.  It includes a free edition that even handles auto-routing.  The board size in the free edition is rather limited and there is also a 2 side limit.

The Result

In the end I had two boards made.  I pulled the memory chips off of the ISA VGA cards and added them to my new 4 Chip memory board.  I plugged in the memory board into my CoCo and crossed my fingers and, success on the first try!  My 4 chip memory memory board is still working in my primary CoCo 3 system today.

 For more pictures see the attachments below: