Chipster

Prototyping the hardware

Modern chips are designed using high-powered workstations that run very expensive chip simulation software. However, the fledgling Amiga company could not afford such luxuries. It would instead build, by hand, giant replicas of the silicon circuitry on honeycomb-like plastic sheets known as breadboards.

Breadboards are still used by hobbyists today to rapidly build and test simple circuits. The way they work is fairly simple. The breadboard consists of a grid of tiny metal sockets arranged in a large plastic mesh. Short vertical strips of these sockets are connected together on the underside of the board so that they can serve as junctions for multiple connectors. Small lengths of wire are cut precisely to length and bent into a staple-like shape, with the exposed wire ends just long enough to drop neatly into the socket. Small chips that perform simple logic functions (such as adding or comparing two small numbers in binary code) straddle the junctions, their centipede-like rows of metal pins precisely matching the spacing of the grid.

The Lorraine prototype, with three custom "chips."
Image courtesy of Secret Weapons of Commodore

At the time, nobody had ever designed a personal computer this way. Most personal computers, such as the IBM PC and the Apple ][, had no custom chips inside them. All they consisted of was a simple motherboard that defined the connections between the CPU, the memory chips, the input/output bus, and the display. Such motherboards could be designed on paper and printed directly to a circuit board, ready to be filled with off-the-shelf chips. Some, like the prototypes for the Apple ][, were designed by a single person (in this case, Steve Wozniak) and manufactured by hand.

The Amiga was nothing like this. Its closest comparison would be to the minicomputers of the day—giant, refrigerator-sized machines like the DEC PDP-11 and VAX or the Data General Eagle. These machines were designed and prototyped on giant breadboards by a team of skilled engineers. Each one was different and had to be designed from scratch—although to be fair, the minicomputer engineers had to design the CPU as well, a considerable effort all by itself! These minicomputers sold for hundreds of thousands of dollars each, which paid for the salaries of all the engineers required to construct them. The Amiga team had to do the same thing, but for a computer that would ultimately be sold for under $2,000.

So there were three chips, and each chip took eight breadboards to simulate, about three feet by one and a half feet in size, arranged in a circular, spindle-like fashion so that all the ground wires could run down the center. Each board was populated with about 300 MSI logic chips, giving the entire unit about 7200 chips and an ungodly number of wires connecting them all. Constructing and debugging this maze of wires and chips was a painstaking and often stressful task. Wires could wiggle and lose their connections. A slip of a screwdriver could pull out dozens of wires, losing days of work. Or worse, a snippet of cut wire could fall inside the maze, causing random and inexplicable errors.

However, Jay never let the mounting stress get to him or to his coworkers. The Amiga offices were a relaxed and casual place to work. As long as the work got done, Jay and Dave Morse didn't care how people dressed or how they behaved on the job. Jay was allowed to bring his beloved dog, Mitchy, into work. He let him sit by his desk and had a separate nameplate manufactured for him.

Jay even let Mitchy help in the design process. Sometimes, when designing a complex logic circuit, one comes to a choice of layout that could go either way. The choice may be an aesthetic one, or merely an intuitive guess, but one can't help but feel that it should not be left merely to random chance. On these occasions Jay would look at Mitchy, and his reaction would determine the choice Jay would make.

Slowly, the Amiga's custom chips began to take shape. Connected to a Motorola 68000 CPU, they could accurately simulate the workings of the final Amiga, albeit more slowly than the final product would run. But a computer, no matter how advanced, is nothing more than a big, dumb pile of chips without software to run on it.