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*** Please note: This website (comp-hist) was completed before I found out about Wikipedia in 2002.
Since then I have added material occasionally.
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Special features
from Unisys History Newsletter Volume 5, Number 1, January 2001
"UNIVAC I: The First Mass-Produced Computer" by George Gray
The First UNIVAC

Remington Rand provided the money to finish the UNIVAC. To reduce the financial losses, it cajoled Prudential and Nielsen into canceling their contracts. The first UNIVAC passed its formal acceptance test on March 29-30, 1951 and was turned over to the Census Bureau, which operated it in the factory for nearly a year. A formal dedication ceremony was held on June 14, but coverage in the general press was minimal. The following day, the New York Times ran a tiny, two-sentence article that referred to the UNIVAC as an "eight-foot-tall mathematical genius, designed to meet problems of the United States Census Bureau", but didn't even mention its name.

The central complex of the UNIVAC was about the size of a one-car garage: 14 feet by 8 feet by 8.5 feet high. It housed the mercury memory unit and all the central processing unit circuitry. The outside of the unit was composed of hinged gray metal doors that could be opened to give access to the circuitry racks. In the center of one of the long sides of the unit, there was a clear Plexiglas door to provide access to the center of the system: it was a walk-in computer. The vacuum tubes generated an enormous amount of heat, so a high capacity chilled water and blower air conditioning system was required to cool the unit. In addition to the central complex, there were eight UNISERVO tape drives, an operator console, and a console typewriter/printer. Originally printing was done offline by the UNIPRINTER, which resembled an overgrown typewriter with an attached tape drive. A much-needed 600 line per minute printer (at 130 characters per line) was added in 1954. The comple! te system had 5200 vacuum tubes, weighed 29,000 pounds, and consumed 125 kilowatts of electrical power.

The UNIVAC represented numbers in binary-coded decimal with six bits for each digit. It employed Excess-3 notation where the binary value was three greater than the actual number, so that zero was 000011, one was 000100, two was 000101, and so on. Excess-3 had been used in the Bell Telephone Laboratories Model I Relay Calculator built in 1940. Excess-3 was chosen for the UNIVAC because it simplified the complementing (making negative) of numbers and made the carries come out right for digit-by-digit decimal addition.

The UNIVAC's word size was 72 data bits, which held eleven digits plus a sign, plus one parity bit for each six data bits, giving a total of 84. The mercury delay line memory amounted to 1000 words. Besides numbers, the UNIVAC could represent alphanumeric data (letters of the alphabet and some punctuation marks) using six bits for each character with twelve characters to the word. Codes were assigned for the letters of the alphabet and punctuation marks, such as 010100 for A, 010101 for B, 010110 for C and so on.

The program instructions were six decimal digits (36 bits, excluding parity bits) long, so two instructions fit in each word. The first two digits of an instruction were the function code, the next digit was unused, and the last three gave the memory address. There were 45 different functions. Many of the function codes were mnemonic, that is, they tried to bear some relation to the operation to be performed. For example, A (still indicated by the bit pattern 010100) was the code for addition. Similarly, D was divide, S was subtract, and C meant to copy the contents of the A (accumulator) register into memory. All the functions didn't work out mnemonically: J meant to store the contents of the X register into memory. On the UNIVAC, addition could be done with just one register, in this case the A register, but other operations involved registers which were designated L and X. An add instruction, such as A 0503, would add the value at the stated memory location (503, in o! ur example) to the value in the A register, leaving the result in the A register. The C instruction C 0504 meant to copy (store, in modern terminology) the value in the A register into memory location 504. On the UNIVAC, multiplication and division involved three registers. For example, the P multiplication instruction multiplied the value in the L register by the value in the stated memory location, giving a 22-digit product contained in the registers A and X. Tape input/output used two 60-word buffers designated I (input) and O (output). The input/output instructions provided for both forward and backward reading of tape. The read backward was particularly useful for sorting, where long strings of data were repeatedly written to tape and read back in through successive merges.

The computer had a high-degree of self-checking: all processing was done in duplicate by two sets of circuitry, and the results were compared to be sure they were identical. Donald Marquardt of DuPont recalled: "One of the big advantages of the UNIVAC was in fact the ability to rely on the accuracy of the numbers when they came out.... Now there were some other computers that I used during that same period where I would make two or three runs on the machine and come up with two or three [different] sets of numbers...."

The UNIVAC had the ability to store the control counter value in memory, making it possible for the flow of a program to go to a subprogram and then return to where it was in the main program. While the 72-bit word could accommodate numbers up to 11 digits, scientific calculations quite often involved larger numbers. To take an example from chemistry, Avogadro's number (the number of molecules in a mole of gas) is 6.02 x 10**23 ; computers could represent this in what is called floating-point format, where part of the word contains the value (6.02) and part of the word contains the exponent. Later computers would be designed with electronic circuits to perform calculations on numbers in floating-point format, but the UNIVAC did not have hardware instructions of this sort. Floating-point calculations could, however, be done by means of software subprogram, making it possible for the UNIVAC to do both scientific computation and business data processing.

Early in the design of the UNIVAC system, Eckert and Mauchly had recognized that for the computer to be useful in handling the large volumes of data used in many business applications, such as payroll of inventory control, it would need to have a high speed input/output system. Since punched cards would be slow, the company developed the UNISERVO tape units to be the primary input/output devices for the computer. Each unit was six feet high and three feet wide. The UNISERVO used metal tape: a 1/2-inch wide thin strip of nickel-plated bronze 1200 feet long. These metal tape reels were very heavy: not the sort of thing for an operator to drop on his or her foot! Data was recorded in eight channels on the tape (six for the data value, one parity channel for error checking, and one timing channel) at a density of 128 characters per linear inch of tape. The tape could be moved at 100 inches per second (as compared with 1.875 on today's cassette tape players), giving a nominal! transfer rate of 12,800 characters p er second. Making allowance for the empty space between tape blocks, the actual transfer rate was around 7,200 characters per second.

No punched card devices were provided with the UNIVAC, so the UNITYPER data entry machine was developed. The data entry clerk typed on a keyboard, and the UNITYPER recorded the values on a reel of metal tape. This lack of integration with punched card systems became a marketing handicap. Many prospective customers already had significant investment in tabulating card systems. When IBM entered the computer business, it made sure that it offered computers that fit easily into existing card processing installations. To fill this gap, Eckert-Mauchly developed a stand-alone card-to-tape unit, which could process 100 cards per minute. Since Eckert-Mauchly was an independent company at the time the design of the card-to-tape converter was done, it naturally followed the market and built a machine that handled IBM's 80-column cards. Sometime after the acquisition by Remington Rand, a version to handle 90-column cards was developed.

from Al Reiter March 9, 2008

I looked at you url and notice that you say the A instruction added the contains of memory to the value in rA. That is not the way it worked, you had to load rX first. Then the A instruction would add rA and rX and put the answer in rA. rA was the dominate register, it had a lot of circuity to get at the bits that performed the computations. I explain this in my web page which you have no doubt looked at. Use google and type in univac reiter. It is the one with the netscape site. I recently updated it to Part 1 and Part 2. Al Reiter. PS: I knew Derek Zave who worked it my group at Roseville.

Historical Notes

One of the many reasons that IBM ate Remington-Rand-UNIVAC's lunch ;-))
(In a period of about 5 years !! - from Snow White down to one of the seven dwarfs - )
This segment is from pages 36-40 of an excellent history of Seymour Cray and his career.
The Supermen: The Story of Seymour Cray and the Technical Wizards Behind the Supercomputer Charles J. Murray (Author)


The purchase of ERA was a curiosity to the engineers at the old Eckert-Mauchly facility. They were unsure what ERA did. They'd heard something about ERA making cryptologic equipment for the navy, but they were unclear how the objectives at the St. Paul glider factory fit in with those of Philadelphia. Most of the engineers in Philadelphia were openly disdainful of the St. Paul crew. Eckert told Norris he thought ERA was in "the Dark Ages." In Philadelphia they referred to the St. Paul facility as "the factory." When that reference trickled back to the engineering crew in St. Paul, it rankled them. The factory? It was true that the ERA crew referred to their own facility as "the glider factory" but when Eckert-Mauchly engineers said it, it had a distinctly different feel-as if it pictured a band of steelworkers building automobile crankshafts. Whether it was reality or paranoia, or a combination of both, the ERA crew began believing that Eckert-Mauchly engineers looked down their Ivy League noses at them. Every slight was remembered and repeated. Someone had referred to them as "the farmers." The farmers. Of their state-funded, prairie school educations, someone else had coined the term "Moo U." With each slight the gap between the sister divisions grew deeper.

If the Philadelphia group was disdainful of ERA, however, the St. Paul band returned its condescension in trumps. True, they grudgingly admitted, the Eckert-Mauchly crew was more innovative. Some of the features on the UNIVAC I had required astounding leaps in engineering, but the crew's record of reliability proved that they were far better scientists than engineers. That was the one element of justice in it all. In a perverse way ERA was gratified that the Philadelphia theories weren't always successful. ENIAC had been plagued by downtime, and UNIVAC I was lucky if it could sustain a ten-minute run without going down due to a bad vacuum tube or some such thing. In contrast, ERA's Atlas had an extraordinary run of five hundred hours in which it required only sixteen hours of unscheduled maintenance. The technological gap that emerged between the two groups centered on the practical versus the theoretical. It was Ivy Leaguers versus the farmers, and the debate never ceased.

What galled the ERA engineers about the debate was that the theoreticians from Philadelphia never seemed to acknowledge the importance of the practical side. It was as if Philadelphia's job was to explore theory, leaving the issues of building workable designs to lower forms of life. Eckert bluntly told Norris that ERA's creative capabilities simply didn't exist.

The tension between the two groups reached a peak when Eckert visited ERA to discuss new ideas for a commercial machine called the 1103. The engineers in attendance were quizzical at first, wondering how Eckert could discuss a design that was so close to completion. When he proceeded to spend an entire morning and part of an afternoon lobbing brilliant ideas at them, the ERA engineers were appalled. They sat in stony silence on their metal folding chairs, wondering how he could possibly expect to incorporate new theories in a nearly completed machine. Eckert, who was known for his blustery ego, sensed their reticence and exploded. "What's the matter with you people?" he barked. "I've been standing up here all day throwing out new ideas, and no one's said a word." But the farmers sat quietly, eyeing him with their stony midwestern stares. Afterward, they privately confided to one another that Eckert's outburst served as a metaphor for all his company's problems: Brilliant as they were, the engineers in Philadelphia wanted to keep the design unbuttoned until the last tense moment, and in the process Eckert-Mauchly had eventually ruined their reliability.

When Norris took the helm as general manager of the UNIVAC Division, he learned that the differences between the two operations went beyond petty name-calling; they reflected profound disparities in philosophy. "The difference," he told the Philadelphia group, "is that you people run a laboratory, and ERA runs a business." The principals in Philadelphia were interested in raw speed and didn't particularly care about reliability. Worse, they had put themselves in a financial tangle by bidding less than one-fifth what it cost to build the UNIVAC I. Later when building a computer called the LARC, they would spend $19 million on a project for which they had bid $2.85 million.

The navy had forced ERA to toe a financial line by setting up a cost-plan-fixed-fee arrangement and then planting itself on the premises in the Naval Computing Machine Laboratory. With Eckert-Mauchly now answering to Norris, the intimidating farm boy from Nebraska, the brilliant theoreticians from Philadelphia were forced to toe the financial line, too.

In mid-1953 Bill Norris asked Willis Drake to go to Louisville, Kentucky, for two weeks to oversee installation of the world's first on-site commercial computer, the UNIVAC I. For an engineer who'd begun his career in St. Paul, as Drake had, it was a strange request. The UNIVAC I was designed and developed in Philadelphia, and in a sense it was a winner in the race to be the first commercial machine - and a St. Paul employee was being asked to oversee its installation. But Drake understood that the walls between the two organizations must one day collapse, and he agreed to go.

When he arrived in Louisville, Drake was first dazzled by the accommodations that had been made for the new machine. General Electric, the first customer, intended to proudly display UNIVAC I in a special site at its Appliance Park facility. GE planned for tremendous news coverage - the machine was purchased as much for public relations as for real computing. As a result, it built a gleaming new showplace for UNIVAC I: floor-to-ceiling glass walls, multicolored drapes, huge potted plants, and spot-lights, all designed to solidify GE's image as a technological leader.

But the real surprise that awaited Drake went far beyond the building's decor: much of the UNIVAC I was missing. The UNIVAC I, dark and quiet, sat in the middle of its vast new showplace, surrounded by cardboard boxes. And inside the boxes was . . . nothing. Remington Rand had delivered a box of electronics and little else. There were no input or output systems, so GE's programmers would have no way to put in data or take out data. The card-to-tape reader, the tape-to-card reader, the high-speed printer - all were missing.

Drake was perplexed. Here he was with only half of a UNIVAC I to install. A whole machine was a rat's nest of wires and contained thirteen thousand vacuum tubes. GE had spent millions of dollars on it and had already orchestrated substantial press coverage. And after the press coverage died down, GE would expect the machine to work. Its users were already putting together programs for business applications: payroll, inventory control, production scheduling.

Drake called Remington Rand's Philadelphia offices, but was told that none of the missing equipment was ready. For several weeks he worked with GE managers, explaining the problems involved in the installation, and in the beginning the managers waited patiently He pushed the operation dates back, and GE reluctantly accepted the new dates. Still, the parts failed to arrive.

Drake meanwhile called John Parker, who now worked as a vice president in one of Remington Rand's New York facilities, urging and begging for the missing parts. The situation was becoming awkward, he told Parker. There'd been mountains of publicity. The press wanted to see UNIVAC I in operation; GE wanted to run its payroll and production programs. Parker seemed surprised. "Gee, the card-to-tape was due to ship last Wednesday" he explained, but there was a last-minute change and they felt it would enhance your liability [as printed in the 10th edition] if they put that change in before they sent it. And as long as it's this late anyway ..."

Drake was appalled. Each week there was another problem with the delivery of the card-to-tape system, or the tape-to-card system, or the printer. And each week the engineers in Philadelphia seemed to be tweaking the design just a little bit more. The original two weeks had now stretched to three months.

Finally GE's Appliance Park manager, whose patience was at an end, called Drake on the carpet. "Either this equipment is going to be here on this date, or all this stuff is going to be out in the middle of the street, and I'm not kidding you," he said. Panicked, Drake purchased a plane ticket with his own money and boarded a flight to Philadelphia. He entered Eckert-Mauchly without an appointment and introduced himself, asking to see the card-to-tape converter and the high-speed printer. He showed them a letter from John Parker, promising a delivery date that had long since passed.

The engineers shot glances at one another, gazing at Drake as if he were speaking Italian and they'd forgotten their Italian-English dictionaries. One of them led Drake to a Ping-Pong table with electronic parts scattered across it. "That," he said, "is the card-to-tape converter." The printer was even farther behind schedule. "I don't know where in the hell you got any dates like that," he said. "This isn't going to be ready for a year." The Philadelphia engineers, Drake thought, acted as if the input-output devices were mere details, that they'd already completed the important part.

Drake hustled out of the Eckert-Mauchly facility and boarded a flight to New York, where he cornered Parker. He told Parker about the card-to-tape converter, the printer, and the Ping-Pong table. He explained the position he was in, the waning patience of GE management, and the lack of any concrete solution. Parker listened in disbelief. Then, to Drake's amazement, he responded, "You're wrong." Parker stood up, ambled across his office, and pulled a letter from a file, showing Drake that the systems were supposed to be ready. Drake was incredulous. As far as Parker was concerned, the memo said the parts would be ready, so they must be ready. It was as simple as that.

For Drake, it was the ultimate learning experience. The fiascoes continued, deadlines were missed again and again. Drake remained in Louisville two years before his two-week project ended. Ultimately, the machine worked, and GE obtained years of use from it.

The lessons were obvious: The years at the glider factory, under the guidance of the navy, had taught ERA engineers how walk a fine line between evolutionary and revolutionary product development. They knew how to use research without becoming researchers. They were engineers, and as engineers they'd learned to build machines that worked-reliably and on time. For that, they didn't need a giant conglomerate or a rich parent company.

The problems at Appliance Park were an example of how far the engineers at the glider factory had come. If this was the state of the art in the commercial market, carving out their own niche wouldn't be difficult.

This Artifact
  • The museum has a UNIVAC I mercury delay line memory
  • some other cabinet(?s?)

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Updated April 24 2003