Today we return to the 1970s to look at one of the most interesting computers sold as a kit during those years. “The Ferguson Big Board” was, as its name suggests, a huge printed circuit board full of chips capable of running CP/M 2.2, the most popular operating system of the time. Based on a Z80A and equipped with 64KB of RAM, it had video output, an interface for 8-inch floppy disk drives, serial and parallel ports, a keyboard, and the possibility of expanding its ROM. Later, under license, Xerox would turn it into one of its most successful models: the “Xerox 820”.
The Altair 8800, popularized in the mid-1970s, had changed the way people imagined computers. They had gone from being huge contraptions confined in large climate-controlled rooms (and as expensive as an ocean liner) to being small boxes, full of lights and switches, that anyone who set their mind to it could buy and take home. However, using or programming something like the Altair 8800 or IMSAI 8080 was still a complicated task, to say the least. That generation of computers, at least during the early years, did not have a keyboard, monitor, or command line that would allow an enthusiast to interact with the computer in a more or less comfortable way.
Jim Ferguson, one of those true electronics geniuses whose name appears very rarely in history books, designed a computer based on the same philosophy as the ones mentioned above, but with great differences in terms of its capabilities. Christened (for obvious reasons) “The Ferguson Big Board”, it was a huge printed circuit board that Jim sold along with a couple of manuals and a list of all the chips that had to be bought and inserted into the empty sockets to turn it into a computer. That was the side of the “Big Board” that resembled the Altair 8800.
But while the Altair 8800, its descendants, and its clones were large boxes full of expansion cards (essential for obtaining a few KB of RAM and being able to connect disks and a video terminal), the “Ferguson” had everything on a single board. On board the Big Board were a Zilog Z80A microprocessor running at 2.5MHz, 64KB of RAM (32 chips of 2KB, model 4116 or compatible), and an interface for connecting two 8-inch floppy disk drives compatible with the SA800 standard from Shugart Associates. Having all that in other computers sold as kits required several boards and a lot more money. But the Ferguson Big Board had more to offer.
The large board designed by Jim had everything necessary for the user to interact with it, without needing to code everything in binary using switches and lights. A composite video output allowed a video monitor to be connected directly to the board, providing 25 lines of 80 characters of text. Today that may seem limited, but remember that commercial computers of the time, such as the Commodore PET or the early Apple computers were not capable of doing the same (except by adding third-party hardware).
Two serial ports, which the user mounted only if they considered it necessary, allowed the Big Board to communicate with the world. A terminal could be connected to them, consisting of a monitor and a keyboard, turning the board into a full-fledged computer.
There was also a parallel port compatible with Centronics, to which one could connect a printer from the many that were beginning to appear on the market. In short, a simple board measuring 8.5 x 13.75 inches (21.6 x 34.9 centimeters) contained a complete computer. It was truly a “big” board, but remember that in those years a simple 8-inch floppy drive measured 9.5 x 14.5 inches, so the “Big Board” was not a monster either.
Many users were interested in this system and Ferguson sold quite a few boards. As is often the case, the boldest began to design expansions for the machine, and shortly after, a publication called “Micro Cornocupia” appeared, which, through a Spartan design, offered program listings and articles exclusively for this computer.
The Big Board had in its ROM a monitor called PFM-80, which acted as the system's frontend. It was really a very good program and allowed using the machine without other software. Obviously, if you had the disk drives, the CP/M 2.2 operating system opened the doors to a whole world of possibilities, allowing thousands of applications to run, almost all of them free, written by disinterested hobbyists and companies years before Bill Gates and his friends even imagined something like DOS. To give an idea of how free programs were in those years, it is enough to mention that the complete listing of the PFM-80 appeared published in the first two issues of Micro Cornocupia.
Four empty sockets allowed adding as many EPROM chips, 2KB each, with extensions many times very interesting, the most common being interpreters of FORTH and BASIC. Xerox, a company we have already discussed, made a deal with Ferguson to use its design in the popular computer “Xerox 820”, something that undoubtedly speaks to how good his work had been. And it was not the only company interested in this great board. Without acknowledging it (or paying a cent to its creator), other big brands based their computers on the Big Board. For example, the motherboard of the Kaypro II is so similar to the Big Board that one has to make a huge effort not to consider it a blatant copy.
As with other computers sold 30 or 40 years ago, the complete circuit of the computer was provided (even IBM did it in 1981 with its IBM PC), which allowed “copying” part or all of its design, something that explains such a profusion of “unofficial clones”. In 1982 Ferguson put on sale the “Big Board II” (BB II), which included many of the expansions proposed and developed by hobbyists. A 4MHz CPU, hard disk interface, connection for ASCII keyboard, possibility of handling 5.25-inch floppy drives, and 6 sockets for ROM expansions were some of its features. We have not yet been able to put our claws on a BB II, but we do not lose hope of being able to do so.
Practically unknown, even among 8-bit computer enthusiasts, the Ferguson Big Board is an important piece of the history of personal computing. Did you know about it?
For more information, see Wikipedia.
