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Zenith 5-S-29
StevenJohnson.com

The Ferguson Big Board Computer
Z80 Processor Running CP/M
by Digital Research Computers

In the early 1980's the Ferguson Big-Board computer was offered by Digital Research Computers as a bare board, a kit, or a ready-to-go populated board. It was powered by a Z-80 processor with 64K of RAM and designed to run the
CP/M operating system.

Since home computers had not arrived yet, I decided to build a Ferguson "Big Board" machine running CP/M so I could do work at home. I purchased the bare board (un-socketed) for $125.00 which came with a parts list, specifications, and schematics.

The Big Board was just that. All I got was the circuit board. I had to track down the parts, power supplies, switches, connectors, cables, disk drives, keyboard, and then build something to put it all in.

It took me a couple of months to track down all the parts and ICs for the board. I decided to socket the entire board so it would be easier to troubleshoot and replace the ICs.

Click on images for a larger view
Big Board Ad
Ferguson Big Board Ad

It took another couple of months to find and order all the additional items needed to make this a functional computer to use at home. I purchased two Tandon 8" floppy disk drives, a Keytronics keyboard, and a Zenith "amber" composite monitor.

The Z80 board, the disk drives, and keyboard all needed cases. When I got tired of soldering, I would work on the cases that everything would eventually be mounted in.
The Ferguson Big-Board and Power Supplies
My Ferguson Big Board mounted in the case


I milled the face of a blank case to mount the keyboard in and machined blank rack panels to mount all the switches, I/O connectors, fuse holders, cooling fans, and disk drives. The front and rear panels for the board and for the disk drives were mounted on a metal chassis. They were then installed in oak cases with the power supplies. Every power supply voltage for the Big Board and the drives is monitored on the front panels using green LEDs.
Back Panels
The CPU and Disk Drive Enclosure Back Panels

After $1,000 in parts and working on my Big Board for almost a year from the day I received the board, it was time to connect everything and turn it on for the first time.

To my amazement (and everyone else)
IT WORKED!
And it kept working with no problems.

I ran the Big Board at home for a year before the company I worked for switched from S100 Buss CP/M machines to the new DOS based IBM PCs. My CP/M Big Board was now obsolete.
My CP/M Computer
My completed Ferguson Big Board

My big Board eventually wound up in the attic. Actually, several moves and several attics. In the Spring of 2006, someone in a forum asked if anyone remembered the Ferguson Big Board. I smiled as I read it and decided to take a trip up to the attic.

25 years after building it, I brought it down,
dusted it off, hooked it all up, and plugged it in.

IT'S ALIVE!
It still works...

Let's see, B to boot, STAT to check the drives, now where's that WordStar disk?

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