Historical Document · 2007
Oral History of John Blankenbaker (2007)
Blankenbaker on his career, SEAC, the design of the KENBAK-1 and selling it. CHM X4068.2007.
Historical Document · 2007
Blankenbaker on his career, SEAC, the design of the KENBAK-1 and selling it. CHM X4068.2007.
Oral History of John Blankenbaker Interviewed by: Lee Felsenstein Recorded: June 14, 2007 Chadds Ford, Pennsylvania CHM Reference number: X4068.2007 © 2007 Computer History Museum Oral History of John Blankenbaker Lee Felsenstein: -- 14th 2007. We are in the home of John Blankenbaker, in Chadds Ford, Pennsylvania. I'd like to start by asking you, John, first of all, where were you born, and date of birth? And tell us something about your family. John Blankenbaker: Okay. I was born in 1929 at the start of the Depression, in Oklahoma. My family was a farming family, largely in dairy and cotton. Of course, for the dairy business, we grew alfalfa, corn, wheat, for feed for the animals. And times were not easy, but we did well enough. Perhaps the severest limitation on the family was that we did not own the land. It belonged to a Native American. So in 1937, the family decided to move to Oregon to a farm that belonged to a cousin of my father. And so for the first seven years I lived in Oklahoma, and then for the next sixteen years, I lived in Oregon. Felsenstein: May I ask something about your parents… about their background? Blankenbaker: My father was always a farmer, though he had a strong interest in becoming a minister. And as a matter of fact, he did one year of work at a seminary, started a second year but fell ill, so seriously ill that continuing the year was impossible. My mother was a schoolteacher and they met at the church in the nearby town. Felsenstein: And so your upbringing was a farm upbringing for the first seven years? Blankenbaker: Very definitely. Felsenstein: Yes. Blankenbaker: [laughs]. We lived on a farm. The only knowledge that I had of town life was at my grandfather's in Apache, Oklahoma, population several hundred. So not a very sophisticated town, but that was my alternative, but basically as a farming family. Felsenstein: Was the family comfortable or was it hardworking or both? Blankenbaker: Well, it was hardworking. Dairy farming is twice a day, seven days a week. Now, since we left there in 1937, when I was seven years old, I was never involved in that work level. But my father, my older brother, my mother, were very heavily involved in work. And though there was free time for activities, my mother was active in a club, did a lot of quilting, and they were very active in the church. Felsenstein: How many brothers and sisters did you have? Blankenbaker: I had one brother that was ten years old than I was. And so I was almost the start of a second family. And then I was followed by a younger brother two years after my birth. So there were three of us, three children in the family, but as almost two families. Felsenstein: I see. You attended school, I imagine, before you moved from Oklahoma? CHM Ref: X4068.2007 © 2007 Computer History Museum Page 2 of 54 Oral History of John Blankenbaker Blankenbaker: Oh, that's correct, I did start in Oklahoma in a four room school, divided in pairs of grades. And when I moved to Oregon, I was then in one and two room schools, until I graduated from the eighth grade. And I have some admiration for those one and two room schools. I enjoyed them very much because as long as you did your work, and didn't make any noise, got your homework done, you could do anything you wanted to do. So I took advantage of the library, read quite a bit of history that was one of my favorite topics to read. And to this day I enjoy reading. Felsenstein: Farming is always, I wouldn't call it a technology intensive occupation, but nonetheless there's a fair amount of technology of different levels. Can you remember any of the technologies that were used around the farm then? Blankenbaker: Oh, yes. First off, we had no electricity. So for example, this meant the cows were milked by hand. Okay, we did have a telephone, and it had a coded signal -- four longs and two shorts, the old party line. Later in life, when we had a telephone that rang only when the call was for you, I was very puzzled. How'd you know it was for you? [Laughs] So, the technology on the farm was mostly power: tractor, bailers, hammer mills for grinding grain. Felsenstein: And so the major power source was not electricity, since you didn't have that. Blankenbaker: That's correct. Felsenstein: And so what was it? Blankenbaker: It was tractors and horses, the major power source. Felsenstein: Okay. So it'd be a gasoline tractor, and there was a power takeoff or something like that. Blankenbaker: Right. It was the Fordson tractor, as I well remember. And my brother just sent me this last Christmas a model of such a tractor. Felsenstein: You would have lived through the Dust Bowl of 1935. Do you have any recollections of that? Blankenbaker: I have no recollections of that. And in western Oklahoma it was very severe. Where we lived some years maybe the rain would be insufficient. The real problem was that prices for farm goods were low. They were very low. And though we were never hurting, it was impossible to get ahead. I think my parents would've liked to build a new home, but it was just impossible to get that far ahead. Felsenstein: So are there any particular memories that stand out from that time, which may or may not have any relevance to your later years? Blankenbaker: Well, there are four events that I remember from those days in Oklahoma, that show that I did have a natural curiosity. One, I'd observed that a jar of water, that the water level went down with time. And I filled the jar up again and made again another experiment and found that it went down. And CHM Ref: X4068.2007 © 2007 Computer History Museum Page 3 of 54 Oral History of John Blankenbaker so I asked my parents about "Where was the water going?" Could've been that the dogs were lapping it up or something of this nature, but it had enticed my interest. Another time I was curious as to what was inside a .22 bullet. And the obvious thing to do was take it apart and find out. So, on the concrete porch, I laid the .22 bullet and started beating it with a hammer. It went off. I ran around the house one way and my family ran the other way, until they caught me. They found that I was quite safe, but it had been a little bit of excitement. It never discouraged any investigations, but perhaps I should've been a little more cautious about it. Another thing that was a puzzle at the time was the Bon Ami can, that was a powder cleaner, and you may remember that on the Bon Ami can there's a picture of a girl carrying a Bon Ami can. And the Bon Ami can of course had a picture of a girl carrying a Bon Ami can. So this recursion went on indefinitely, and I was very puzzled about how far it could go. And it's not how far they carried it out, but it seemed like to me that it was sort of never ending. I didn't understand the word "infinity" then, but I was very bothered by this whole concept. Another thing that has had a big influence on me is that some summers in Oklahoma it's very warm. So warm that it's better to sleep outside on the ground. So we would spread the blankets on the ground and we'd go to sleep there. And looking up at the sky I'd see these stars. Now we were far enough away from any big city that you had good visibility. I was very, very impressed at that time, and I remain impressed today, by the Milky Way, and the number of stars in it, and what that represents, and where we are in this larger picture. And perhaps that had some influence on me, I don't know. Felsenstein: Did you parents encourage your explorations in any way? Blankenbaker: My mother was a very strong advocate of education, of reading, and something of this nature. But they didn't particularly encourage physical things. They were tolerant. At a later time, I took my mother's washing machine apart, to see how it was assembled, at least a portion of it. And put it back together again. But my mother who was aware of what I was doing didn't raise any objections, so there was a certain tolerance on their part to my experiments, my efforts and explorations. Felsenstein: So you were seven when the family moved, is that right? Blankenbaker: To Oregon, I was. Felsenstein: Okay. And so then what was that environment like? Blankenbaker: [laughs]. Well, we moved to a farm that was sight unseen. We found out when we got there that it was half a mile off the road through the woods. And it had no electricity and no phone. Perhaps we knew that, but I don't think we understand clearly that it was so far off the road. So at seven years old, I was marching through, or walking through the woods to get to school, had to walk to school about a mile-and-a-half. Not all of it through the woods, but it used to scare me a little bit. Felsenstein: Well, certainly there're not many woods in Oklahoma, I imagine. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 4 of 54 Oral History of John Blankenbaker Blankenbaker: Oh, not to the extent that there are in Oregon. But there are definitely woods. We owned a farm in Oklahoma, had woods, and -Felsenstein: So, my stereotype is of complete pool table surface and so forth, not true. Blankenbaker: Yes. Felsenstein: In Oregon, how are things different aside from the physical environment? Blankenbaker: Not a great deal different. Still, it was, on this poor farm, it was pretty hard making a living, and so we did a lot of work off the farm. And let's see, I guess when I was still seven years old, we picked hops one summer. Hops, as used in beer, which at the time had to be picked by hand. And my younger brother and I, while we were on the hop-picking venture, had to pick a basket, which is about four feet tall, full of hops every day. Our pay for this was an ice cream bar each. Felsenstein: But were you four feet tall at that time? Blankenbaker: [laughs]. I was four feet tall, but we were just barely above it, the basket. And we could hardly move the basket. Felsenstein: I see. Blankenbaker: We picked the hops one at a time, which was hardly the way to get rich fast. Felsenstein: Then so you attended a slightly larger school, did you say? Blankenbaker: No, slightly smaller schools. They were one and two room schools. The first one in Oregon was two rooms. On another move that we made, it was a one room school, where I went for three years, I think, skipping one year. Felsenstein: When was the skipping? What year was it? Blankenbaker: Fifth grade. Felsenstein: Okay. So you were, your family was still renting? Blankenbaker: At the time, we were still renting, until 1943. So for six years, we rented, and not all of that time were we farming. But then in 1943, my parents bought a farm, and all of this is in very much the same neighborhood. Felsenstein: What was the town? Blankenbaker: Albany, Oregon. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 5 of 54 Oral History of John Blankenbaker Felsenstein: In the Willamette Valley. Blankenbaker: You're right, very good. Felsenstein: My sister lives in Portland, and my father lived in Eugene. Okay, so tell us more about your own intellectual development, and your interest in technology, how that developed in your upbringing. Blankenbaker: Until I was in high school, I have no clear recollection of any outstanding event. In high school, it was fairly typical. I did work on automobiles, on our automobile. I tore an old automobile apart, down to the last nut and bolt. I started driving to school as a licensed driver when I was age 14, because the high school did not provide bus service. You had to get to school on your own. So I drove the family car and the head of the school board signed a certificate stating that I needed a license to get to school. So, it was very typical. I read "Popular Science." I built battery powered radios, but we did have electricity by that time. Such activities were fairly typical. Other activities and high school, I was in two plays, enjoyed that tremendously. I tried running the mile in track, which I did not enjoy. Came back the next year as manager, which was a more pleasurable activity. Felsenstein: The tearing the car apart, why did you do that? Blankenbaker: Well, the car was so old that it was of no value and I was curious, a little bit, about the parts of a car. I'd basically understood by then how an internal combustion engine worked, and among the things that I read during this period of time, are the college textbooks of my older brother. The one that I found most enjoyable was Business Law, when I was probably ten or eleven years old, not even in high school yet. But I read other books about mechanical engineering and so on. Felsenstein: So that was an exploration, just to sort of see what the car was made out of, is that correct? Blankenbaker: Oh, that's correct. Yes. How the parts are put together, the parts of it. And I saved the nuts and bolts and segregated them as raw material for future projects. Felsenstein: Okay. The radios you worked on, tell us something about that, and I would like you to be as technical as possible. Blankenbaker: The first one was just simply a one tube radio, battery powered, nothing complicated. Then I tried paralleling the two tubes to see if I couldn't get more power. And strangely enough, no it didn't. [Laughs] The radio basically brought in, I think, two stations, the local stations, though once when electricity failed, I brought in Salt Lake City, which was just an amazing, to me, my one tube radio, would bring in a station from that far away, when the local stations were off, were blacked out. Felsenstein: You'd need an external antenna of course. How long was yours? Blankenbaker: As I seem to remember, I went to the roof of the barn and ran a wire down toward the house. And I had done that earlier because I'd tried building a crystal radio, and I put that antenna in for it. The crystal radio didn't work, in part I think because the earphones sold to me were bad, and nonfunctional. I never did make it work. But the one tube radio receiver had a very conventional circuit. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 6 of 54 Oral History of John Blankenbaker Felsenstein: Was this a regenerative circuit or just a grid detector? Blankenbaker: It was a grid detector, yes. Felsenstein: Okay, and what was the tube number in it? Blankenbaker: I have no recollection. [Laughs] Felsenstein: Oh, okay. Did you follow it with other radios, or that was it? Blankenbaker: No, that was the only one. Having built it and saw that it worked, I wasn't that much concerned to go on and do anything more elaborate. Felsenstein: And there was the failure of the parallel tube experiment. Blankenbaker: [laughs]. I asked around some people that I thought, my physics teacher and another student in the school who did a lot of work with radios, as to why it didn't improve the volume. They gave me quite unsatisfactory answers, they didn't know. Of course it was a question of impedance matching. And it really didn't change much of anything. Felsenstein: So, proceed and talk about your education in high school, for instance. What were the main areas of study, or did you get any choice in it? Blankenbaker: Oh, yes, there was a choice, and I took the curriculum that was called "College Preparation." There were even choices within that, but I'd had the science electives, which meant biology, chemistry, physics; I took all of the mathematics that was offered, which went through calculus; three years of English and then Social Studies. Felsenstein: So you elected the kind of scientific sub-curriculum of the college preparatory curriculum, is that correct. Blankenbaker: I did, yes. Felsenstein: Why? Blankenbaker: That just seemed to be of most interest to me. Though when I was in the ninth grade, I wanted to be a draftsman; as I went further my sights were then a little bit higher, though it was by no means clear how I was going to afford college. In the spring of 1946, when I was a senior in high school, and thinking about college, and not knowing how I was going to afford it, a Navy recruiter came to the physics class and explained that the Navy had an Eddy Test and that if you passed the Eddy Test, they would send you to eleven months of electronics school And you could sign up for only two years. And at the end of that, you had four years of college. Obviously, I took the Eddy Test, I passed it very easily. I was enlisted in the Navy, and so began a new phase of my education. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 7 of 54 Oral History of John Blankenbaker Felsenstein: Okay. So tell us about that, for instance the Navy and the technical school. Blankenbaker: Okay. They sent me to Great Lakes, north of Chicago-- that was boot camp for two months. Following that, we commenced about seven months of what was called Primary School, and there was a lot of fundamental work: resistors, circuits, vacuum tubes. The ultimate event was that we build a radio receiver. And so we studied radio receivers and transceivers and built a radio receiver with several tubes. That was followed by another school in Washington, D.C., that was about three months long and we studied there the advanced equipment: radar, sonar, loran, and some other things of this nature. So, 15 months after I had joined the Navy, I was now ready to go to work for the Navy. Felsenstein: As an electronics technician? Blankenbaker: As an electronics technician, third class. And this was besides the technical experience that we had in school, it was an eye-opener to me in several ways, for this farm boy that had never experienced the big city life, to visit Chicago, the art museum, Museum of Science and Industry, Washington, D.C., The Capitol, the White House, Williamsburg, things of this nature. All of these were broadening of my experience, besides the technical training that I was getting in the Navy. Felsenstein: Did you learn much from your fellow sailors? Blankenbaker: Nothing much from that, it was the school that was basically responsible. Many of them were very interested in radio, and so on, but I observed that their knowledge, their experience, was really very limited. And it was all swamped out by the technical characteristics of the equipment that we were learning. And so after 15 months, and I was ready to go to work for the Navy, they assigned me to a destroyer in England. An American destroyer, it just happened to be in England. They got me there eventually, and I commenced work largely on radar. It turned out I think there were five third class electronic technicians onboard the ship, and no one any higher than that in the electronic technicians. So, there's very little direction, it was left to you sort of to find the work to do and to do it. And I had no problem. I worked on all kinds of radars, had a lot of fun about it. I even worked on the fire control radar, until they told me that that wasn't my responsibility that was another department, the fire controlman. I worked on electronics; I worked on mechanical aspects of it, and so on. But we were back in Newport, Rhode Island, and altogether on that destroyer was not more than about five months. And then the destroyer was slated to go on a midshipman cruise to the Mediterranean. I volunteered to stay in beyond my enlistment, if they would just let me go on the Mediterranean cruise, give me a bunk and food; they didn't have to give me any pay. But they said no. They said if I wanted to sign over, sign up again, they'd give me a promotion, and I could go on the midshipman cruise. But I said no, I joined this navy to go to college, and I was going to go to college. So, it was back to home, back to Oregon State College. Felsenstein: One question, you were apparently the most competent technician of the five, would that be fair to say? Blankenbaker: I think that's true. Felsenstein: And did there arise any, I want to say hierarchy, but that sounds too official, but I'm saying, did you rise to the top or was it a matter of your just keeping to yourself? CHM Ref: X4068.2007 © 2007 Computer History Museum Page 8 of 54 Oral History of John Blankenbaker Blankenbaker: Everyone was independent. I kept to myself. I did my work; I didn't attempt to influence anyone else. Most of the others did really nothing. And so the electronics officer, who was not involved on a daily basis, did tell me later that he had, in the report of how long it had taken me to adapt to or become a useful member, had given me a period of two weeks, and he said he had never given anyone that short a time. So, I perhaps made some impression on the officers from the very beginning because the first project that I worked on was a wire tape recorder. And the wire had broken, but there were instructions about how to fix the wire. And I did so. The officers found out about it, took it up to the wardroom, and had great fun playing with it, broke the wire, would bring it back to me the next day, ask me to fix it. They'd take it up to the wardroom, the wire would break again. It was not a highly technical-it was not a good product. Felsenstein: Not rugged. Blankenbaker: Yes. But I worked on some transmitters and some receivers. There were some electronic countermeasures. I was studying the Morris Code a little bit. I did once, listening to a very slow sender: B-O-S-T-O-N, Boston! I got so excited I never returned to the subject. But again, yes you could send information this way. I had proved it, I had received the word Boston, but I sort of lost interest in it then. Just typical of many things that I did. After I proved it, one tube radio receivers, I lost interest. After I received the word Boston, I lost interest. Felsenstein: So that should keep you moving in some direction. So where did you go? You went to college next, right? Blankenbaker: Yes. I returned home and I went to college, and I enrolled in physics. The question was "Should I be in physics or should I be in electrical engineering?" I took aptitude tests on two different occasions, and the net result is, they said, "Oh, yes, yes, those are good choices, but have you thought about architecture? Have you thought about chemistry? Have you thought about teaching?" Which didn't help me at all because I was trying to get some guidance as to what I should be doing. So I had enrolled in physics, I stayed in physics. It would have been possible to switch to electrical engineering without any difficulty. In general, I liked the concrete a little better than the abstract, but I could stay with physics until we got to particles [laughs] got to Schrodinger's Equation much later and so on. So it was in physics. I had a lot of credit from the Navy work. Oregon State gave me a lot of credit. So, I had no problem at all in piling up enough credits for both physics and mathematics. And I was interested enough in mathematics to be taking it. I still had credits left over and I had taken some more German, I could've had a B.A., also. And I was so interested in other subjects that I wanted to sample them: philosophy, psychology, sociology, religion. I did take some German. All of these things, but I didn't pursue. Again, I sampled, find out what they were about a little bit, and then sort of lost interest. Felsenstein: Now this was OSU, where was the campus? Blankenbaker: Oh, the campus is at Corvallis, Oregon, there in the Willamette Valley, not far from Albany where we lived, so it was only 20 miles to college, though I did live on campus all the time. Felsenstein: Good. And you were enrolled in Physics. Blankenbaker: I was enrolled in Physics. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 9 of 54 Oral History of John Blankenbaker Felsenstein: And did you graduate in Physics? Blankenbaker: I graduated in Physics and in Mathematics, two Bachelors degrees. Felsenstein: And you could have had a third there, you said? Blankenbaker: I could if I worked a little bit harder and had a third. I did try some stupid things like taking too many courses. One semester, or term, I tried 21 hours. 16 was normal, 18 was outside, and I tried 21. I had such conflicts that I couldn't even go to the chemistry lectures, which resulted in my only C. But I didn't get all that many A's. I wasn't that great a student. I was interested in a lot of things, but I wasn't entirely, that I'd want to go into things in that much depth. Felsenstein: Tell me a little about any extracurricular interests. Blankenbaker: I was in a couple plays. That was about the extent of extracurricular activities. Oh, aside from playing chess, or something of this nature. I debated one term, I guess it was. One thing that was extracurricular my freshman year, is that I happened to read, in I think it Popular Science, about this new computer, as they called it, this roomful of equipment, with thousands of vacuum tubes, and only two numbers, zero and one -- strange combination. Well, the thousand vacuum tubes didn't discourage me too much, because when you've worked on a radar that's got maybe a few hundred in it, it's not a far stretch of the imagine to thousands of vacuum tubes. It was a little stretch of the imagination, though, only two numbers, zero and one. I'd never heard of such a thing. So, going to work, I figured out how I could write a number with only zero and one; how I could convert that to and from decimal; how I could do arithmetic in binary. This wasn't entirely just an academic exercise, because in the Physics lab, we had to do a lot of computations, and they wanted you to use logarithms. Now, most engineers and most physics students carried slide rules. Usually we faked it, that is we got the first three digits maybe from the slide rule, and we added a fourth digit or something of that nature at random. But here was a computer, maybe I could make a computer. So this was my motivation for studying this binary number system, and I think I went so far as to work out how I could make an arithmetic unit. And though I don't remember all the details of it, I do remember that it had a novel device in it. I say novel in the sense that something I'd never seen before. I was thinking of electromechanical devices because that's something very concrete. Vacuum tubes are a little bit abstract, the relay seemed very concrete. My novel device was based upon a rod which had two stable positions, and it could change positions by rods that came this way that were energized by electromagnetic coils. I didn't realize it at the time; I learned later that it was a JK flip-flop. The memory was to be relays, and it was not a stored program computer. I was perfectly willing to turn a crank, to select the operation, to turn a crank, to select the memory, this bank word that I was talking about. So it became time to add up the cost. Now, remember, that all I had basically was my GI Bill, which paid books and tuition and something towards living expense, and I had maybe $1000 that I'd saved from the Navy. Well, it was obvious that I couldn't afford this device, and so I lost interest in it, and never did anything more with it. But I was impressed by computers as an intellectual exercise. It was something to be interested in. Felsenstein: And you essentially developed binary arithmetic just from the concept of ones, the basis of one and zero, or did you read up about it? CHM Ref: X4068.2007 © 2007 Computer History Museum Page 10 of 54 Oral History of John Blankenbaker Blankenbaker: Oh, no, no, everything I worked out just on scratch paper myself. I had never read anything about binary numbers, and I don't know that I ever did, really, so to speak. They weren't taught in school, and it was not a subject that a lot of people talked about. No, it just, by how do you write a number with zeros and ones, how do you do arithmetic, how do you convert it to decimal? To and from decimal? So, it was just, I worked it out. And I'm embarrassed, though I smile at it happily now, how long it took me. It really took me several days to work out these simple things, which now I guess grade school students understand -- or some of the better ones do. But at the time, I didn't know that it was taking me such a long time to do this. [laughs] Felsenstein: Well, it would seem that, I can certainly attest that I would never even have tried, because I had an older brother to instruct me in everything. Blankenbaker: [laughs] Felsenstein: But your older brother was far beyond you, so you had to do it yourself, so I congratulate you for that. Alright, before we approach your employment years let's try to concentrate on what more you can say about your college experience. Blankenbaker: Between my junior and senior year, I applied for a summer intern job, with what was then called the National Bureau of Standards. And I did get a position. There were a hundred of us interns, and four of us were assigned to something called SEAC, which stood for Standards Eastern Automatic Computer. This was based, I guess, upon the EDSAC. It was operational. It'd been operational about a year. It was probably the most useful computer in America at the time -- the most powerful, and the fastest. A serial machine, still yet, but it was in use seven days a week, 24 hours a day, lightning permitting. It was sensitive to thunderstorms. It was during thunderstorms that private individuals could maybe try a program, if they understood that sometimes it might not get any result. Felsenstein: Where was this job? Blankenbaker: Oh, this was in Washington, D.C. It was at the Bureau of Standards main campus, which is north part of part of town, northwest part of town. And I felt so lucky that first I even had the intern job, and that I was one of the four chosen. And I wondered, "Why was I one of the four chosen?" So when the personnel office in the course of the summer called me in for an interview about how it was going and this, that and the other, I was bold enough to ask, "Why was I selected for this job?" because I felt so lucky. He says, "Oh, you had lots of chemistry." [laughs] Felsenstein: [laughs] Blankenbaker: Well, first his logic was wrong, and I hadn't had a lot of chemistry. [laughs] And I thought, let's just drop it, maybe they'll take me out. [laughs] I was anxious to stay there. The work was trivial, the assigned work that we had, but the opportunity to learn a little bit, of course, was great. We were introduced to Boolean equations, logic, and I did get late in summer my opportunity to write a program. Felsenstein: [John holds up a portrait] Let’s take a look at the picture of you at age 18 That was just prior to discharge, you said from the Navy. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 11 of 54 Oral History of John Blankenbaker Blankenbaker: That is correct. Felsenstein: Okay. Blankenbaker: I was at Newport, Rhode Island. An artist in the USO made this drawing. And I sent it home and lost track of it until my brother found it and sent it to me just, oh, less than a year ago. And my wife liked it so much that she asked for it as a Christmas present. . Felsenstein: Okay. Now, where we left it was the summer intern position with, you said, was it National Bureau of Standards? Blankenbaker: Well, that was what it was called then. And today it is called National Institute of Standards and Technology, I believe is the modern name for it. Felsenstein: You said that the work you were doing there was trivial, but the work that was being done there was what? Blankenbaker: Oh, they were solving problems for everyone else in the government. I imagine that the Atomic Energy Commission was there with a lot of work for them to do. But as I understood it, it was for all kinds of agencies. Incidentally, the computer was still having a few little problems. They had to trim up the signals in the delay lines, and sometimes they did not quite have the trimming just right. Debugging, as I understood it was very difficult. It had to be done with an oscilloscope. You could not look at a word in memory. You could not study anything that way. All you could look at is those wave patterns on an oscilloscope, which meant that it was a little bit difficult to do. Felsenstein: Tell us about the design of that computer. I think you mentioned a serial. Blankenbaker: Oh. The original machine was serial based upon mercury delay lines for the memory. There were 512 words. They were very long words, some where in the order of 50 bits. I am not sure about the exact number. It was a four address instruction, alpha, beta, gamma, delta, two operands, a result, and the location of the next instruction. And it was binary all the way, of course. Input teletype, output teletype. Later they decided to try a new memory, or add a new memory, 512 words of CRT memory, or Williams tube memory, where the information was stored as a spot in the phosphor on a CRT. And a screen on the exterior of the tube could detect, when you tried writing again, whether there was any information there already. There was a slight difference, but it was not reliable. At first the programmers rapidly converted all of the programs over so that they take advantage of this random access memory. It was much faster than the serial memory of delay lines, but it was unreliable. And later on they went back to the mercury delay lines as being reliable. Felsenstein: My understanding, which is no doubt imperfect, of the Williams tubes, was that it was a refreshing memory. It was a dynamic memory. Blankenbaker: That is correct. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 12 of 54 Oral History of John Blankenbaker Felsenstein: And that I thought that the information was simply scanned sequentially in a raster pattern and then repeated. Blankenbaker: Well, that was the refreshment would probably be that way, but if you wanted to access any one word for operations, you could go directly to that word. Felsenstein: So you could, in effect, direct a beam to a particular bit, I suppose. Blankenbaker: Yes. In parallel to all the bits of the word. Felsenstein: Right. So there would be N tubes if there was an N width word. Blankenbaker: That is right. And the room where they were stored, all the faces of the tubes were staring right at you, or you were staring at them. Actually, it would have been, if they wished, it could have been the modern pixels with a display on the tubes. They could have done that. The 512 words, let’s see, that is 2 to the 9th, so 5 by 4 is another 512 positions. You are right, which would have been 5 by 10, or something of this. Yes. Felsenstein: Yes. Alright. And in fact it was not like the IBM version, where there was a metal plate over the face, the tube. You could actually see them. Blankenbaker: There was a wire screen. Felsenstein: I see. Blankenbaker: It was still visible. The dots were still visible. Yes. Felsenstein: But you say they were not reliable because other effects, lightening at the very worst. Blankenbaker: Yes. That made everything unreliable, not just the Williams tube. Felsenstein: Right. Okay. So the main memory was delay line or Williams tube. Blankenbaker: Yes. Felsenstein: And there was a mathematic logic unit of some sort clearly. Blankenbaker: Yes. About which I really know nothing that I could say, except that it was a serial machine, and it was fixed point. Felsenstein: Okay. Your duties in regards to this were what, anything? CHM Ref: X4068.2007 © 2007 Computer History Museum Page 13 of 54 Oral History of John Blankenbaker Blankenbaker: The interns, the four of us, were building packages that had these little delay lines, a fraction of a second, you know, and sometimes packages of diodes for the logic. I was given the assignment out of the four of building a tester for these diode packages, so that you could plug in a package and test whether all the diodes were working. Felsenstein: So you were in the most fundamental level building logic modules, not very sophisticated, I imagine. Blankenbaker: Yes. All of them were passive modules. There were vacuum tubes, but we had nothing to do with vacuum tubes. We were building the passive components, logic modules. Felsenstein: What year was that? Blankenbaker: 1951. Felsenstein: You graduated with your bachelor’s degree when? Blankenbaker: 1952. Felsenstein: And then where did you go to work? Blankenbaker: Okay. At the conclusion of a senior year, I still had the job at the Bureau of Standards if I wished to return there. I applied one other place. I applied to Hughes Aircraft Company because they had a very special program that you could go to school half time and work half time, and get a master’s degree. It was at UCLA. So I applied to Hughes Aircraft Company. They were into many kinds of activities, but I very fortunately, again, was assigned to a digital computer department. And that was an eye opener in itself, because they had a digital computer that was the size of a small suitcase, and it was for aircraft, for flying aboard aircraft. So after the roomfuls of equipment that I had seen in pictures or had seen at SEAC, which was several rooms of it, this was very impressive. And the machine was fairly easy to understand, too. Felsenstein: This was military equipment? Blankenbaker: Yes. MMAX 79. I think I can repeat the number today safely enough, can even remember it. Felsenstein: This is very interesting. I mean, we should not be surprised but, in fact, in 1952 they had a computer of that size, vacuum tube or transistor? Blankenbaker: It was still vacuum tube. At that time it was a little peanut tube, which was even smaller than my finger right here and diodes. Incidentally, diodes were still considered so valuable then that at night you had to make an inventory of the diodes in the lab, and all the free diodes had to be returned to the safe. And that is how valuable diodes were at that time. CHM Ref: X4068.2007 © 2007 Computer History Museum Page 14 of 54 Oral History of John Blankenbaker Felsenstein: These are geranium diodes. Is that correct? Blankenbaker: I think they probably were. That was still at that time. You are right. And Hughes was building geranium diodes. They were in the business of doing that. They were a leader at the time in that geranium diode. Felsenstein: Were they point contact? Blankenbaker: I think they were. They must have been. They mush have been. I just do not have a clear picture in my mind. Felsenstein: Okay. So what was the work you were doing there? Blankenbaker: The first few months was nothing much. I was introduced to several things, but after about three months the Hughes Aircraft Company formed a department to build a business data processor. “John, you would like to work on that?” “Yes.” “Well, you will design the arithmetric unit”, a binary coded decimal, serial machine, drum, magnetic drum memory, vacuum tubes. Even that, you see, still vacuum tubes, diode logic. I had no experience designing arithmetric units really, in spite of my interest in it. But no one else did, either. Felsenstein: So that would answer the question of why you. The answer is, no, there was no one else. Blankenbaker: That is right. Felsenstein: And you had studied something about binary. Blankenbaker: I knew something about binary, yes. And many of the other people had some knowledge and, again, it was another one of those luck of the draws, like being assigned to SEAC, going to Hughes, assigned to a digital computer project, then on the business data processor, being assigned to do the arithmetric unit. So it was learning on the job, and these were big, expensive machines. This machine had a motor generator that was like this in diameter, the motor and the generator. [John holds up his hands very wide] Blankenbaker: And the whole object of this was merely to filter the power in that because it took 60 cycle power in, and it generated maybe 400 cycle power or something, but it made the task of filtering the DC