I came across this little machine in a roundabout fashion - 4kW of RAM and 1usec cycle for "under $10,000"! (not including ASR33)

It seems this is largely lost to history. Does anyone know what this machine was made for (it seems all too similar to many other systems of the era, why bother?) and if there are any notable uses? I suspect they built it for internal uses?

Some of their marketing suggests there is a "700 series" of which the 704 is a single member, but if there are any other members of the line they are definitely lost in time.

The only reason I heard of it was that I talked to Rick Loomis some time ago and he mentioned this was the machine he bought to run Flying Buffalo.

UPDATES: Apparently there was a 706, but I can find no details. In the meantime:


  • 3
    Ooh, hardware multiply and divide Sep 22, 2021 at 15:40
  • 4
    From the information I found (Google "raytheon 704 minicomputer"), it seems that this was built for general automation tasks. Things you would perhaps nowadays do with a single-chip controller.
    – chthon
    Sep 22, 2021 at 16:45
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    @JoelReyesNoche: I suppose it should mean 4 kilo Words...
    – chthon
    Sep 23, 2021 at 9:33
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    In the early 1970's, there was a Raytheon 704 in the corner of the computer room at Rolls-Royce Derby Engine Division (where they made and tested jet engines). I never saw it being used (except by me to learn machine code programming). Probably it was used occasionally, but certainly not very often. The main computer was a Raytheon 520 (discrete germanium transistors!) which collected and analysed data from the engine test rigs. I was part of the repair & maintenance crew there.
    – NL_Derek
    Sep 26, 2021 at 21:09
  • @NL_Derek - great, now I have ANOTHER article I need to write... Sep 27, 2021 at 14:01

4 Answers 4


I might be the only person on StackOverflow who used this machine!

I wrote tens of thousands of lines of Raytheon 704 assembler code in the 1976-1978 timeframe. We used it to run an air traffic control simulator system used by the Canadian government, and for other purposes. It handled input from a bunch of workstations and drove simulated radar displays.

It was a pretty capable system from what I recall. Was my first job so I didn't have much to compare it against.

I still have the user manual!

Edit: in addition to the ASR-33 teletype, the system also supported 9 track tape drives. We used to edit our source code by reading it in from one tape, editing it in memory, and writing it out onto a second tape drive. You had to be really careful not to mix up the tapes - we always used the write-protect ring.

The editing was done using a CRT display and keyboard - don't remember the manufacturer, but it was uppercase only. We wrote the editor ourselves.

  • 4
    Very cool to have an answer from first-hand experience. Welcome to retrocomputing.se! Jun 28, 2022 at 2:41
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    This seems to be the primary use, radar data processing and air traffic control in a variety of places. Jun 28, 2022 at 12:05
  • I found a photo! See new answer below. Aug 17, 2023 at 15:27

According to the Raytheon 704 Technical Manual:

The processor may be used as the control element for data acquisition, data processing, and system control. (p. 1-1, section 1-7)

An example of something you could do with this class of computer would be automating the control of a fresh water treatment plant, starting and stopping pumps as needed to keep water levels and pressures correct, monitoring various equipment for alarm conditions such as over-temperature, and so on. Among the list of peripherals available were ones that you would need to interface the computer to the world in order to measure and control things, listed on p. 1-4:

  • Buffered digital output channel (e.g. starting pumps)
  • Buffered digital input channel (e.g. is that pump running?)
  • Digital to analog converter (e.g. what speed should a motor run at?)
  • Digital plotter controller (e.g. make graphs of water pressure over time)
  • 4
    There were lots of process-control minis kicking round in the 1970s. I suspect every vendor had to have one :-)
    – dave
    Sep 22, 2021 at 22:42
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    Digital process control started at the tail end of the 1950s. Computer vendors all came out with systems tailored for that market (think about how many processes there are that need control). By the mid-to-late 1970s, there was a realization that no one really wanted to program control systems, and that packaged programmable systems were the path to the future. Distributed Control Systems (DCSes, like Honeywell's TDC-2000) and Programmable Logic Controllers (PLCs) took over the market. But control-oriented mini systems were a big thing for nearly a decade
    – Flydog57
    Sep 23, 2021 at 18:09

I was an engineer in the 70s / 80s - expert in PTS100, 706, 704 and RDS500.

I worked for SITA; these machines were used for communications - with multiplexers for modems (2400 baud - 9600 baud) and for message switching of low speed telex and tty traffic.

The 700s were almost identical in logic, SSL, but the 706 was a drawer with flat backplane and all the chips plugged in - debugging consisted of finding the busted component.

The 704 was not as brutal - they rearranged the logic over a series of plug-in boards which meant it was very much easier to fix with less downtime, but essentially the same machine. Curiously, the 704 was a later design, and slower.

The PTS100 in all its iterations was designed to be used in offices with lots of terminals attached (through 1 inch thick cables) - the big cabinets could host I think up to 64 terminals.

Similar design but different purpose were the RDS500 series - replacements for the 700s.

The PTS100 and the RDS500s were engineering nightmares. All the boards fit horizontally into the backplane. In a full blown dual processor RDS500 configuration there were over 40 muffin fans. Software was all in assembler on a real time pre-emptive OS. Primitive.

I knew those machines so well - such is youth!


I found a photo! This would be circa 1977.

enter image description here

  • In addition to the ASR-33 in the foreground, there is a punched card reader (mounted on the back wall) and a keypunch machine. Aug 17, 2023 at 16:58
  • 2
    It might be a good idea to add it to your original answer instead of making a second.
    – Raffzahn
    Aug 17, 2023 at 18:48
  • Is this your own photo? I’d love to put it in the wiki article. Aug 24, 2023 at 17:53
  • Yes it's my photo. Feel free to use it. Aug 26, 2023 at 2:00

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