A Contribution from Don Watson

Don Watson

Nearly everyone has at least one personal computer now, but this wasn't so when I worked at the Lawrence Livermore National Laboratory. I'll try to tell why and how I came to obtain the lab's first personal computer. If my memory fails in parts, I'll tell the story as it might have been.

I arrived at the lab in 1965 as a senior scientist in Bio-Med, and worked there until 1973. After graduating from medical school in 1959, I took a three-year post-doc in neurophysiology at Albert Einstein College of Medicine. Computers were novelties in biomedical research then, and none of the available systems were well suited to the tasks at hand. Thus, having spent some time watching J. Macy wrestle a CDC 160 into submission, I concluded the struggle was so burdensome, and the rewards so disappointing, that the care and feeding of the computer overshadowed any research project I might imagine. If that was to be the role of computers in neurophysiology research, I wasn't interested.

In 1963, I went to the University of Washington for two more post-doc years in membrane biophysics. A few months before I moved to Livermore, I met George Michael on one of his periodic trips to Seattle. George enthralled me with tales of big computing at the lab. Though I was awed with the promise of big computers for big science, I didn't expect to ever be involved with them. I was engaged in small science. Besides, by the time I met George, I had already developed big ideas about small computers.

Walt Woodbury, my mentor, and Al Gordon were selected to evaluate the LINC (Laboratory Instrument Computer) under real working conditions. I didn't get hands-on experience with the LINC because no one could dislodge Walt and Al from the console. Still, I watched over their shoulders and heard their gleeful shouts when the machine dutifully obeyed their commands. I was hooked.

The LINC was radically different from big computers such as the CDC 3600s that arrived at the lab in 1962. People who focused on computing tools were intrigued with large and fast machines, and they seemed blind to the possibilities of small computers. This was understandable. Small computer development seemed to be moving in the wrong direction. Instead of the 48 bit words of the 3600, the LINC operated with 12 bits--like the then-ancient CDC 160. Instead of the 32K memory of the 3600, the LINC had 4K. Compared with the 3600's gait, the LINC lumbered.

Focusing on the tools, however, could easily overlook the tasks. This point had not been lost on LINC's designer, Wesley Clark of MIT's Lincoln Laboratory. He saw advantages in small computers for laboratory research, especially in electro-neurophysiology. Principal virtues included small size, low cost, flexible I/O, accessibility to the researcher, and a user-friendly programming language. These features, Clark figured, could qualify a small machine as a central tool for research projects that entailed collecting and analyzing large numbers of discrete, time-dependent data.

The foresight of LINC's developers would be recognized in a 1992 ceremony when the LINC at the Massachusetts Eye and Ear Infirmary finally retired after 28 years of continuous service.

The enthusiastic early reception of the LINC by neuroscientists propelled DEC to develop its own versions of the device. They first attached a LINC processor to the PDP-8, their own minicomputer, to make the LINC-8. Then, in 1969, DEC announced the PDP-12, a single processor machine that supported the instruction sets of both minicomputers, and could be switched between them while a program was running to optimize I/O or computing operations.

As soon as I saw the PDP-12's specs, I decided I needed one for my work and play. The machine had a 12-inch CRT display, two LINC tape drives, and sixteen analog inputs for A-D conversion, eight of which were driven through preamplifiers from conveniently located potentiometers. Though the basic machine included only 4K of core memory, the random-access tape drives allowed virtually unlimited storage by allowing overlays of data stored in 256-word blocks.

My requisition for the computer elicited a hearty belly laugh from my boss, Bernie Shore. But I insisted that I needed it, and Bernie always took our needs seriously. He warned me that my request would need approval by Computations, where it would probably die. Now, here I must guess what happened, not because my memory is fuzzy, but because I never knew. I like to think that the decision makers approved it because they realized that their expertise in computers did not qualify them to evaluate the technical needs of my laboratory research. And, perhaps they were interested in discovering what a small computer could do. What I know is, the decision was made, and the computer was delivered a few weeks later.

Knowing nothing about hands-on programming, I was dismayed to find that the machine's documentation was limited to two manuals, one with the PDP-8's instruction set, and the other a user's manual for the LINC and DIAL editor/assembler. Nevertheless, these turned out to be sufficient, and before long, I felt confident that I could make the machine do anything it was capable of.

My collaborator, Don Yee, and I used the PDP-12 to study the electrochemical properties of silver-silver chloride electrodes in solutions containing both chloride and iodide. A typical run produced a second-order curve superimposed on a linear segment. I programmed the computer to collect and save voltages, then to display these data points on the CRT. After manually setting boundaries on segments of the data with the A-D pots, I used least-square statistics to determine the parameters of these elements.

The computer made this analysis far better than any we could have made otherwise, but it didn't produce hard copy. But thanks to the rapid turnover of peripheral equipment at the lab, I was able to reap the spoils of salvage. I found an X-Y plotter, for which I wrote a driver-including English and Greek character sets, and this gave me the hard documentation I needed.

In my mind, though, I wasn't using the full potential of the PDP-12. I envisioned writing a program with which I could write and print our papers. The printer that came with the machine, an ASR-33 teletype was, of course, wholly unsuited to this job. So I went back to salvage and found an IBM Selectric. A Bio-Med engineer (I wish I was better at remembering names!) designed and built an interface for the typewriter, which provided excellent printed text. Since the dedicated Wang word processor didn't appear until 1971, I figure that my program was one of the earliest word processors--if not the first--to run on a general purpose computer. Of course, it didn't occur to me that anyone else might, one day, find use for such a program!

I don't want to leave the impression that I simply made the machine do lab work. That would have been cruel for such a bright, versatile, quick learner. I had heard of BASIC, and I thought it was a good idea for ad hoc calculations and plotting. So, I played with code, using the PDP-8's floating-point software and LINC's I/O abilities, until I came up with a fairly versatile interpreter. But it was slow and cumbersome. In other words, my interpreter resembled BASIC, not only in its operations, but in its dynamics.

How important was my PDP-12 to me? It was far more than a tool. It was a friend. When I left the lab to start my psychiatric residency, I grieved for my human friends I was leaving. But, mainly, I grieved for my PDP-12. That's why I call it a "personal" computer.