Siemens SICOMP M-series

One of the computer systems least probable to find information about on the Internet is probably the Siemens SICOMP-M series.

SICOMP-M "minicomputers" are more or less mainframes which were used as Terminal servers, for controlling production and for data storage.
The machines have been built from the early to the late 80s. Because of their reliability they were often used in nuclear plants, in the automobile production or for controlling satellite uplinks. A UNIX called "Co/X OS" could be run on them after adding some optional RISC-based coprocessor card. Not to forget: low CPU consumtion due to intelligent peripherals - all in all a sturdy little system :)

The hardware

  • CPU based on MOS-VLSI and Fast-TTL integrated circuits
  • 16 bit CPU operating at 37,5 MHz
  • system bus clocked at 10 MHz
  • 64 kB cache (32 bit)
  • can address up to 8 MB ECC-DRAM modules (1 MBit)
  • CPU speed about 3600 Dhry/s^2 or 970 kWhets/s^-1 (32bit)

    Lots of interesting feartures: During power outages the RAM contents would be be kept for up to 12 hours (3 hours garanteed) by means of an internal battery. Some memory areas can be locked from access by the processor by means of a turnknob, these locked sections can then be manually addressed as private memory.

    SICOMP M80 machines The picture at the left shows two SICOMP M80 machines, which were used as terminal and database servers for a laboratory of the Uni-Klinikum Erlangen. The machines needed its own air conditioning system - nothing unusual back then, the CPUs drew about 2000W / 220V, the HD boxes about 1700 Watts / 220V. Each container had two powerful (and noisy) fans built in. Even FD044 8" floppy drives consumed about 180W these days..

    Measuring about 55x120x80 cm they weren't small either - and surely not lightweight (about 250 kg each). Though being large does not mean being slow or unusable. The M80 was quite superior. It could manage up to 11 SCSI-I/SCSI-II harddrives, 300 MB each. It also contained a 5.25" floppy drive, a tape streamer and some MO-drive which was added later (594 MB).

    Interesting hardware features included a buffered realtime clock, a timer (alerting the system using interrupts) and a periodical alert for starting those system jobs that needed to be run from time to time.

    SICOMP M80 frontpanel Some DR205 type printers were attached to it, really large beasts with sound proof casing. The DR205 was able to print up to 1760 characters per second and could print graphics and barcodes as well.

    The picture at the right shows a large (and unfortunately quite shaky) shot of the front panel of one of the CPUs.

    Attached to the M80s were about 20 Siemens "Sichtstation DS 075 B" terminals ("Sichtstation" means "video terminal"). The screens were quite large (about 15") and the fonts could be read comfortably. At the bottom of the screen two lines were reserved for displaying status information. The screens were available with display colors white, green, orange and paper white. As an option a graphics extension (including mouse and graphics tablet), RGB connectors, an internal magnet card reader, a barcode reader and a key switch for access control were available. The DS 075 was even available with a DEC vt220 emulation! Of course all terminals come with automatic screen blankers for preventing burn in.

    Sichtstation DS 075 B The terminals are quite lightweight (13kg - keyboard: 1.8kg!) for their size, but seem to be incredibly clumsy and take a lot of space due to their shape and size (about 32cm high, 41cm wide, 35cm in depth). Of course this is not only a disadvantage. I was told those old Siemens terminals are very quite easy to service as everything is well accessible and easily taken apart.

    It seems they can't be used with any other machines than the SICOMP-M series as they run a highly proprietary protocol named "DK3964R" ("LAUF"-procedure). This is similar to the block mode known from IBM mainframes. The serial lines of the terminals (V.24/V.28, X.27 or 20mA/TTY lines at up to 19200 baud) were connected to so-called serial PROMEA-MX-cards which were located in the container of the M80 itself and in some add-on box to which the system bus was extended. Due to intelligent I/O-management the subjective performance of the machine is very high. As an example, 50 terminals, 30 line printers and 40 serial ports controlling machines can be attached to an M70 without any trouble, the CPU will not hit its maximum load. The manual says the M80 can serve up to 80 TTYs.

    Some interesting I/O cards

    The MX-cards are not the only interesting hardware extensions. Besides the basic serial I/O cards ("PROMEA") which could process 256 byte at once including protocol processing, the system had a 1.5 MBit/s fiber optics interface ("DU02") which used a HDLC-based transmission protocol. Maximum length of the fibre line was 2 km.

    There also were two 10 MBit ethernet cards, DU03 and KS100. While the DU03 card only processed the OSI-1 and OSI-2 layers, the KS100 card was advanced enough to process OSI layers 3 and 4.

    The DU06 I/O card supported HDLC (and SDLC) via V.24/V.28, V.36/V.11 and X.21/X.27 at a speed of up to 72kBit/s and could be connected to DatexP, DatexL or ISDN networks.

    Other devices available for the system but not found in the particular installation i visited were MB60 reel tape drives for 1/2" tape (730m/150 MB, 120-470kB/s, 1800 Watts) and PS 048-B hard disk platter drives (250 MB MFM/12 platters, 1200 kB/s, 2000 Watts).

    Operating Systems

    There are two operating systems available for the SICOMP-M series: BS-M and AMBOSS-4. While BS-M focuses on real time applications AMBOSS-4 is somewhat more office-centered, concentrating on user interface and applications. AMBOSS is short for "Allgemeines Modulares Benutzer-Orientiertes Software System" (this translates to: "univseral modular user oriented software system")

    The particular system this page describes was running the "AMBOSS 4.0" (BS4) Operating System. Both userinterface and databse of the lab system was completely written in FORTRAN, the hardcopy of the source filled numerous binders.

    AMBOSS offers multitasking, 10 priorites for programs to run at, and some sort of I/O quota. Additionally, it offers a spooling system that operates using virtual devices. At max. 4094 processes can be simultaneously. Each process is identified by program name or process number. Process priorities can be specified at program start or during execution. Without segmentation the maximum size of each process is about 130kB.

    Files are identified by device and filename. Within the libraries (some sort of directories which may only contain files, but no other libraries) files are identified by specifying device, libary-type (data/text/source/...), library name, filename and version of the file (similar to VMS). Files could be protected by means of write-protection, ownership and some sort of group mechanism.

    Regarding processes, the system can give information about type, size, priority, state and segmentation. Concerning the CPU the system gives information about CPU-consuption of the OS (system), CPU-consumtion of the user processes (user) and idleness of the CPU.

    Each system has some a system console called "Standartmeldegeraet". Certain OS commands can be restricted to this console by specifying border program numbers - programs with IDs below the border may only be run/controlled from the console. The "shell" is called "Standartbedienprogramm" (short: SBP; it means: "standart operating program"), though it is no real shell - more like a mixture of menues and forms/prompts as far as I found out. Logging of errors, system calls and I/O operations (log-level can be specified) was done to a file or log printer.

    Among the programming languages available for the system were C, Pearl (no typo!), Fortran and Cobol. There was some interesting editor named "MEDIS-M". Nothing special about it, let alone the fact that there was no need to save the changes done to the file - you edit the file directly on the disk drive, byte by byte!

    Emulating SICOMP M80...

    A company called IKPS even wrote some emulator named PC-SIC/NT which simulates a SICOMP M environment under windows NT. According to their paper on the project the emulator is emulating the hardware itself, i.e. including priority levels and interrupts. The devices formerly attached to the M-system are emulated by seperate NT-processes. An Intel P133 running NT is said to be able to reach the speed achieved by a "real" M80 system. A nice (german) page from Siemens about replacing SICOMP systems with SICOMP emulators can be found here.

    Who uses/used such a system?

    DER SPIEGEL 39/99, 27th of September 1999, 
page 28ff. From a picture which was published in "DER SPIEGEL" (39/99, 27th of September 1999, page 28ff.) it can be seen that M-machines are (or at least were) used for controlling the traffic lights of Berlin until at least September 1999 (see lefthand picture). The president of "Meldepress", the press agency which holds the rights for the photograph, kindly allowed me to republish it on this page. There is no doubt some of the shown screens are Siemens DS-type terminals. The article states that the equipment dates back to 1980.

    According to an article which was published in "Nordbayerische Nachrichten" Wednesday, 22th of September 1999, M-machines are also used for controlling the traffic lights of Nuremberg, Bavaria. Just as in the former case, a Siemens terminal can be seen on the picture. Unfortunately, in contrast to the very friendly and openminded people at "DER SPIEGEL" and "Meldepress", the people at "Nürnberger Nachrichten" (who publish "Nordbayerische Nachrichten") did not allow me to show the picture on my webpage, i'd have had to spend quite some money in order to aquire the rights for the picture first.

    Hearty thanks and greets go out to:

    Heimo Schoen who supplied me with some of the information given on this page
    Mr. Melde from "Meldepress", who allowed me to use the picture published in "DER SPIEGEL".