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Since then I have added material occasionally.
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Manufacturer UNIVAC
Identification,ID UNIVAC-NTDS, CP-642
Date of first manufacture1958
Number produced -
Estimated price or cost-
location in museum -
donor -

Contents of this page:


    (a.k.a. UNIVAC CP-642, 
    UNIVAC 1206, and AN USQ-20) 
    Remington-Rand Univac Division
    Word Length 30 bits
    Speed: 9.6 microseconds add time.
    Primary Memory: 32,768 words core memory (3.6 microseconds access time)
    Secondary  Memory: Magnetic drum and magnetic tapes,
    Instruction Set: 62 30 bit, single address instructions.
    Architecture: Parallel, binary, fixed point arithmetic, 7 index 
    registers, 1  accumulator register, 1 free register. 
    Technology: 10,702 transistors,
    Input and Output: Punched  cards,  paper tape, CRT
    Price: $500,000.
    Size: 58.6 cubic feet, 2,320 pounds, 25 kW
    Software: CS-1 compiler
    Development History: Developed under contract for the Navy 
    Tactical Data System (NTDS) by the Saint Paul division of
    Remington Rand Univac. Seymour Cray was the primary
    logic  and  circuit designer.
    Production History: The first units were  delivered in 1958/
    Later commercially available as the UNIVAC 1206  .
    Use: Real-time tactical analysis, display and control of weapons.       

See The Univac M-460 Computer which appears functionally identical and physically similar to the NTDS computer.

The following images are from "Duane"

Special features

Historical Notes
from Jan Thompson - Jan 4, 2014
I do remember that the flip-flops were all 'discretes' on a 1.25 x 2.25 circuitI board - one flip-flop per card!
I was on the USS Forrestal from 1964 - 1967, which may have been the first sea going installation of USQ-20's (?).

Mike and I taught the NTDS system at Mare Island from 1967 until I was discharged in 1970.

from Don Bryan (540) 949-1394, Feb 2004
Hi Ed,

I was a DS Tech from 1968-1976, and can provide a little more info on your NTDS computer page.
First, the link to the M460 page is nice, but the correlation is not quite accurate. The "bathtub" machine pictured at the bottom of that page, with all the I/O connectors on the left side, appears to be the original NTDS computer, the AN/USQ-17, which was designed by Seymour Cray.
The picture on your page, of the machine with front doors open, and no control panel, is the first USQ-20, or CP-642.
This machine was followed by the CP-642A (USQ-20A) and CP-642B (USQ-20B); both of which featured the control panel at the top of the machine.

For reference, check the book "When Computers Went to Sea", about the development of the NTDS system, and you can verify my information.

Don Bryan

When Computers Went to Sea : The Digitization of the United States Navy by David L. Boslaugh (Author)
List Price: $39.95
Product Details
  • Paperback: 500 pages ; Dimensions (in inches): 1.05 x 9.18 x 7.46
  • Publisher: Wiley-IEEE Computer Society Pr; (April 4, 2003)
  • ISBN: 0471472204 | All Editions
  • Average Customer Review: [4.5 stars]

This Artifact

Interesting Web Sites

Other information
March 3, 2021 - received from Skip Saunders
I Googled USQ-20A, and had a nice time reviewing memory lane of some of the folk who worked with those computers.

In my case, I went to programming school at FCPCPAC in spring 1969. I probably had Gary Atrobus as an instructor, but I can’t recall. As a newly minted Ensign I was assigned across the street at NEL (Navy Electronics Lab….. later named NELC, and later named other things.)

I was the Division Officer for the Anti-Submarine Warfare Ships Command and Control System (ASWSCCS) for 1969 and 1970. I rewrote the tracking module to include a Kalman Filter Algorithm instead of the Alpha-Beta Algorithm used in the original version. The Alpha-Beta algorithm worked fine for tracking objects that had frequent observations (radar targets mostly) but wasn’t good for the infrequent observations made through sonar. If a submarine made a maneuver between observations (something easy to do given the long time delays involved in sonar systems of the day) the tracker would loose lock.

The Alpha-Beta tracker had very high granularity, the object was either in the Alpha bin (flying straight) or in the Beta bin (flying a turn). Consequently, it worked well for objects that were easily observed. However, for a submarine, the boat could easily move out of the Beta bin two or three times without a good position fix.

The Kalman filter used a covariance matrix to estimate the degree of uncertainty associated with an observation, and that degree of uncertainty could be made to expand as time between observations increased. The only problem with using a Kalman filter was the algorithm required a matrix inversion step. The mathematical capabilities of the fixed point calculations in the USQ-20 had a big problem if one tried to divide by a very small number. More often than not, that “small” number would be represented as a zero….and you can imagine the USQ-20 vomiting every time it was asked to divide by zero.

I “fixed” it by ensuring the least significant bit was “lit” whenever a divide by zero situation was encountered and we thus had a functioning, but handicapped, Kalman Filter for tracking submarines in the ASWSCCS version of NTDS. I completed the software development and took a tape to the Wasp, Koelsch, and Voge on ASW exercises in the Caribbean Sea. Thus getting my first carrier arresting hook landing, and later a catapult take-off experience.

I had able assistance from my enlisted division lead by Master Chief Saur. They included Senior Chief Davis, and several E-6’s and E-5’s whose names I’ve now forgotten. They were all good operators and helped substantially with the development of mine and other improvements to the NTDS being pursued by NEL. I wrote most of the code in CS-1, but occasionally used machine code, and later some CMS-2. I think I was one of the first people to use the CMS-2 language, because I tried to put it to use as soon as the first versions of that compiler was written.

For some reason, I didn’t get rotated to Vietnam following my ASWSCCS days. Instead, I was one of four “plank” holders to develop the micro-electronics facility out on Point Loma. My degree from Cal was in EECS and the “ee” part included solid state physics, so while I was able to exercise the “cs” part in the ASWSCCS projects, I was given the chance to build a fabrication plant and integrated circuits for two years in one of the old battery bunkers on Point Loma. --- But, all that is another story. Thanks for keeping memories alive.

April 2020 - received from Jim Wagner
I was cleaning up some boxes this morning and stumbled across my old CP-642B Repertoire of Instructions, or Rep card. In googling the CP-642B just to see what info might be out there I ran across your web site and the wealth of info on that old boat anchor.

Back in 1972 after graduating from programming school I worked for a government contractor (ISSI) at Dam Neck, Va. programming the CP-642B. We were rewriting the NTDS code for a destroyer system. The system was three CP-642B's interconnected with a message switching system for communications. Various program modules did dedicated functions such as navigation, fire control, anti-submarine, radar, tactical displays, etc. All functions were coordinated by each code module sending and receiving messages between themselves based on input from control consoles and shipboard systems.

I was assigned the anti-submarine module to re-write because I had previous anti-submarine experience as a P-3 Orion crewman while in the Navy and understood the tactics.

All testing was done in a mocked up destroyer CIC, usually in the middle of the night because the system was used during the day for Navy training. We got one compile of our code a week. In between compiles we created code patches in machine code and built paper tape patch collections to load over the compiled code for testing. During testing we operated the system the same way the Navy would, testing each available function. That old systems was definitely a "hands on" experience.

After that job I became an IBM mainframe systems programmer and later a Unix version of the same until retiring in 2011.

Good job on your site and thanks for preserving the info on those old systems.

Jim Wagner, Durham, NC

Aug 2018 - received from Lou Lenzenhuber
I was a Data Systems Technician in the US Navy from 1971-1977. My two years of schooling at Mare Island includes the USQ20 system including the CP642A(Univac1206), CP642B(Univac 1212), CP789(Univac1218), RD231 (Paper tape punch & reader), RD243(Magnetic Tape Unit) and UGC-13 modified teletype. Schools also included Hughes Aircraft SYA-4 and UYA-4 tactical display systems and conversion systems including the UNIVAC KCMX (Analog,synchro,digital converter) and various digital to analog and sychro converters.

The two years of school were followed by two years at the school maintaining the equipment used to train Data Systems Technicians. After the Navy I spent two years with Hughes Aircraft Company teaching NTDS to Iranians who never did receive the DD993 ships because of the revolution. I also spent 9 years with Sperry/Unisys maintaining the equipment used to teach Data Systems Technicians at Mare Island. I ended up being familiar with three generations of Sperry-Univac NTDS computers (CP642,UYK-7 , UYK43) and three generations of Hughes Aircraft Display systems (SYA-4, UYA-4, UYQ21) and most all the equipment a DS could be taught in school as well as some underwater fire control systems.

Attached are the Rep Cards for the CP642A&B. A function code of 23 with a K field of 7 is a Square Root instruction on the bravo but doesn't exist on the alpha.

One last thing. On your Univac-NTDS page. An OS1 Jack C Lamb asked in 2008 who programed Star Trek and Battle Wagon for the 642s. The displays showed his initials RLM. He was a Data Systems Technician named Roger Merritt. He showed up on my ship the USS Worden home ported in Yokosuka Japan in late 76 or early 77. I borrowed his galaxy star map and wrote a similar Star Trek program that ran on the UYK7 and UYK43 (in UYK7 compatibility mode) in the 80's while working at the Data Systems Technician School for Sperry/Unisys.

Jan 2016 - received from Guy Fedorkow
... but by coincidence, a colleague loaned me a book "A Few Good Men from Univac" by David E Lundstrom, which has a couple chapters on the author's experiences as an engineer on the Univac NTDS design team.
    I know the [Computer History] Museum has an NTDS machine... do you know what vintage it comes from?
    Wikipedia credits Seymour for the first design, but says his version never made it to production.

January 30, 2013 -
A series of four articles on the NTDS by Robert Clinton, appearing in Jim Strickland's Volunteer Information Exchange, - relative to the NTDS at the Computer History Museum.

Received from Ben Wiedemann - July 2012 - DS on the USS California (CP-642B)
I served as a DS technician on the USS California from 1973 to 1977. I was doing some remenising about my past when I came upon your web site and all the people who are writing you about their experiences with NTDS. So if your' interested.

Schooled at Mare Island, Oh by the way it was my graduation class members that brought Battle-wagon and Star trek to the fleet, or at least to our ship. These games were highly addictive and the reason no one talks about it is because probably like us, we not only played these games, the officers did also.

After some time the Captain got well, angry is a good word. From the very beginning we had trouble with the 642b boxes. All 3 were a nightmare for us. NTDS crashed constantly. We could never run more than 48 hours, and sometimes we would be down in less than 2 hrs. I don't know how true this story is but I was told these boxes were built by Sylvania. I was told, the NAVAL Dept contracted out to have someone else build these computers, that is, at least some of them more cheaply.

Eventually we wound up at Chesapeake into dry-dock for a re-fit. A hole was cut into the side of the super structure and all 3 boxes were booted out. We received 3 overhauled computers and our 3 went back to Roseville, MN. We no longer had problems with NTDS and everything worked pretty well.

Target info was sent via 2 CP-789 (1218) processors to the 4 weapons computers (1219) forward and aft. Status to digital provided by a Sperry Keyset-Central Multiplexor. C&C and IC Switchboard was ratty but functional. Link 11, 14, 4A all worked well. Got out after 6 years.

Received from James Lester - August 2011 - The Old Days: Univac, San Diego, NTDS, UYKs, CMS-2
I was a programmer for Univac at their San Diego facility (FCPCP) from 1963 - 1968 working on various software modules of NTDS. We programmed both the AN/UYK-7 and -20 in CS-1 and CMS-2.
After my time there I went with CDC in La Jolla, CA (real-time hospital/medical and industrial process control applications in assembler and Fortran for the CDC 1105 (I may have the hardware nomenclature wrong - it's been a long time ago!)).
But I finally got back into the business of real-time naval computing applications in 1973 when I went to Pascagoula, MS with Ingalls Ship Systems. We were programming the AN/UYK-7 and -20 in CMS-2 for systems to go abd the USS Spruance (DD963).
From there, I went to Newport, RI with Hughes Aircraft where they were involved with real-time naval systems, this time for SSBs and the Trident SSBN. By this time, Univac had morphed into Unisys which was later absorbed by Burroughs.
I would be very interested in contacting anyone who worked for Univac, San Diego during the 1960s when we were developing NTDS on the UYKs in CS and CMS-2. (It really tickles me to see the movies and tv shows involving modern-day USN at-sea operations which use the NTDS on-screen symbology we developed at FCPCP! There's been virtually no change at all!)
Thanks again, Jim Lester, Arden, N.C.

Received from John Richardson Jan 2011
I had asked "Do you have (unclassified) manuals for the machine?"

No. The documents relied upon the most were the schematics (logic & wiring). These were several volumes and were huge. I can remember having to lay them out on the deck next to the machine being worked on. These computers were actually very reliable, at least the ones on the Long Beach. We would actually do back plane wiring changes that involved pulling out a chassis, flipping it over, removing the cover to expose the three deep wire wrap connections to the 15-Pin card sockets, and actually change the wiring. The amazing part was we'd put it all back together and it would work!!!

Received from Jim Seaman Retired Navy December 18, 2010
As a Navy Electronics Technician (ET) I attended an eight-week school on the East Coast (Dam Neck, VA) in late 1963 where we were introduced to machine language programming of the CP-642. These were used at Patrick Air Force Base in Florida for test instrumentation analysis, Tedious.

Then I was a Chief Warrant Officer (designator 7600), reporting aboard the USS Long Beach (CGN-9) in late 1970 while it was being refueled at Mare Island CA. The job was supposed to be the Communications Maintenance Officer, but I actually worked as the Assistant Electronics Maintenance Officer that included some oversight of DSs that maintained the NTDS equipment. I also stood CIC watches as the SWC (Ships Weapons Coordinator) during two very long WestPac deployments, mostly in the Gulf of Tonkin as the PIRAZ platform. Well I remember the CP-642s (I think there were three of them) with the discrete component circuit boards and the ferrite core memory.

Further along in 1975, as an LDO LT, I went to school at Mare Island to familiarize myself with the Combat System equipment going on the USS Texas (CGN-9) that was being fitted out at Newport News Shipbuilding in Virginia. More machine language. Still tedious. I was the NTDS Officer on the Texas and the DSs worked for me. I Liked the three UYK-7s - We had a completely separate computer room.

and there is more

Received from Bob Boden - Oct 2008
I was the Development Engineering Manager of the Central Computer, Channels, and Operator's console of the FSQ32 computer.

Getting old but still kicking. I now live with my wife Joyce at:

Robert Boden
129 Evergreen Lane,
Florence, Oregon, 97439
541 997 7583

My latest endeavor is the Phondot system.

Received from Lyle J. Franklin - Mar 2008
I was on staff to Vern Leas, NTDS Program Manager, when he made the decision to drop the 17 which was designed by Seymour Cray. At decision time Seymour had already left for CDC and was not involved in the design of the 20. The placord should be corrected. People I remember involved in the design were Finley McLeod, Hy Osofsky, Glen Kregness and many more. Curt Christensen was involved in the decision to redesign. As I remember it, we built serial sixteen first to serve as the prototype. The 17 was supposed to be the NTDS prototypes. Curt has tried to correct many of the errors appearing in the historical documents. Curt can be reached at 651/457-1401.

Lyle J. Franklin
Life Number 5885

Received from Jack C. Lamb - Mar 2008 - 'Battle-Wagon' and 'StarTrek'
I was a lowly, button-mashing twidget (OS) in the US Navy circa late 70's/early 80's and, when we were moored and had a stable power supply from shore, we always tried to talk the DS's into loading up 2 great games that were played in CIC on the NTDS consoles...

I really liked 'Battle-Wagon' and the other was 'Star Trek' or similar. Would you know anything about the history of these early games (i.e. who slipped these to the fleet and who programmed these on the side?)

I doubt the Navy contract for the AN/USQ-17 or AN/USQ-20 'officially' included these diversions (but they were great in their day!) seems no one wants to remember or talk about them...

Thanx!...signed OS1 Jack C. Lamb/USS Luce/DDG-38 (R.I.P.)

Received from Barrett, Joshua - May 2007
I was an OS on the Carl Vinson from 1988 to 1991. We still used 3 CP-642B to run the op program. They came from the Oriscany (I was told)

- - - - later - - - -

they were replaced when the carl vinson went to the yards in late 1990. it is on the chuck boat web site. Thanks!

There is still a CP-642B on the midway museum in San Diego in the SINS room. There is also one at the computer history museum near google in Mountainview CA.

Received from Gary Antrobus - Centerville OH - April 2007
What great memories! One of my assignments as a new officer in the Navy in 1968 was to teach programming for the AN/USQ-20, both machine language and the CS-1 compiler. During the machine language part of the training we used Frieden Flexowriters to punch paper tape for program and test data loads. We had to debug using the register panels on the top of the units by executing one instruction at a time and reading the output lamps. I got so used to base 8 math that it took some time to relearn base 10 after I left the assignment. I still have the laminated instruction card.

The 8 week course we developed was fantastic. A junior officer or civilian could enter the program with little or even no knowledge of computers and two months later could be relatively productive working on the various NTDS modules at either FCPCLANT or FCPCPAC.

I really loved this duty and I got to work with some of the most brilliant engineers and technicians I have ever met. The UNIVAC people and the navy ETs were amazing!

Received from Larry Schneller
I was a Navy DS (Data System tech)from 1961 to 1966. I went to school on the 642A at Mare Island CA. After the Navy I worked for several years at Pt. Mugu where we had a 642 and several 642 Bs. Later they got a 1230 almost the same machine but a few more capablities (developed for NASA).

Some of the info in the write ups didn't sound right right. The memeory cycle time (read/write) on the 642 was 16 micro seconds. The CPU had a 4 phase clock (4 micro secs per phase). This info is about 40 years old. I may have an old Tech manual for the Computers some where. The picture at the web site did not have the maintenace panel which sits on top. I stuck with the Univac computers for years and advanced to the UYK 7 in the 70s.

Received from William H. Bennet received Nov. 10, 2002
Hi Ed,

I was a DS from 1967 to 1974. I had a 1668 job code for computers and peripherals.

The 642A was all germanium transistors. The 642B used silicon. Both had a 1 MHZ clock, divided into four phases. Instructions were from 4 microsec. to 48 microsec., depending on the operation. Memory was ferrite core. Cycle time was 8 microsec., 4 to do the destructive read, and another 4 to write back in from of the Z register.

Both had an unusual hardware square root routine. The op code was for divide (23), but it extracted the root if the k register was 7. The X register did an elaborate shift process, which took 48 microseconds.

I believe your figure for power consumption is high. We ran 3 642A's, a RD-281 magnetic tape unit, the paper tape reader/punch, and several other pieces of gear off one PU-491 motor-generator, rated at 5 Kw. The power supplies were unregulated, and used 400 Hz 3-phase power to minimize ripple.

The fleet had no assembler/compiler, so we had to do our programming by sitting on a tall stool so we could manually enter each instruction into the A register. Each instruction was manually stepped into memory. If nothing else, you learned effecient coding. We wrote some maintence routines, and a few games. I think every DS wrote a patch for War or Spaceship. We also has Baseball and Football. All were played on the Hughes Aircraft radar display consoles.

You can't really apply core technology criteria to these old Univacs. In a way, every manufacturer had a core technology, but things were still evolving from some really primitive beginnings, so I wouldn't think of the differences as such. The distinction between a 642A (Univac 1206) and a 642B (Univac 1208) was pretty slight.

The biggest difference was the change from germanium to silicon transistors. As the germanuim transistors were non-standard, the change probably save Univac significant cost per unit. The old germanium transistors were housed in a grain of wheat sized casing, with fine insulated wired coming out one end. The transistor had to be mounted in a nylon clip, and then each wire had to be stripped and hand inserted into its hole in the pc board. Has to be labor-intensive.

Both computers used PNP transistors, so a logic Low was true, and a High was false.TTL was hard to get used to after I got out of the Service.

The other differences were small. The 642A had more elaborate circuitry for memory. There were manual adjustments for the X, Y and Z drive currents. The 642B had a Z current adjustment only, as I recall. The 642B could have its I/O channels sped up from 125 Kword/sec. to double that rate. Some problems apparently crept in, as there was an engineering kludge in the ODR timing circuit. It was two flip-flops that had been added. One was named Finkbine, and the other Gomez. I noticed that the newer Mil-Standard 802C prints omitted the names.

It just popped into my head that the logic in the 642A was basically all NOR gates, while the 642B was all NAND gates. The prints were reprenented in something called bubble logic, where each element was a circle. 802C was lots easier to interpret.

Without prints and such, that's about all I can recall of these computers. Hope this helps,

Bill Bennett

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Updated August, 2018