How To Install a Hitachi 6309 Into Your Coco

Written by Chris Burke formerly of Burke & Burke.

OK .. due to a number of typos in the previous version, here's the whole thing again. Please discard the old version.

Here's an application note for those of you who are contemplating installing a 6309, but who don't look forward to desoldering the old processor. It explains a "trick" that greatly simplifies installation.

You can stack a 6309 on top of your computer's existing 6809. Here's how...

Cut pin 39 (TSC) of the 6809, leaving a small piece sticking out of the processor so you can solder to it.

Take a 40 pin IC socket. Cut off pins 5, 6, 33, 36, and 38. Bend out pin 39 so you can solder to it.

Stack the 40-pin IC socket on top of the 6809. Solder all of the corresponding pins together. DO NOT solder the pins 39 together.

Now you have two options:

  1. Solder a wire from 6809 pin 39 to +5V, and another wire from socket pin 39 to ground.
  2. Solder a 4.7K resistor between each pin 39 and +5V. Then take a SPDT switch, connect the common contact to ground, and connect each end to a separate pin 39.

In either case, finish up by plugging the 6309 into the socket. If you picked option 1, you now have a 6309 system. If you picked option 2, your system is now switchable between the 6809 and the 6309 (before power-up - not while running!).

I hope this helps some people install their 6309. Good luck!

Chris Burke

Taken from the Canadian Tandy CoCo Home Page