Siemens 4004 computer family

Solving various corporate and technical-scientific tasks

Terminal network operation

SZKI

PMSZK-PSZTI

DATORG

OTP

TAURUS

VIDEOTON

Structure

Central unit

Word processing machine: 32 bpW

• control unit:
  • 16 general purpose (32-bit) registers
  • 32-bit instruction counter register
• main store:
  • 45: 256 KB ferrite ring RAM
  • 151: 512 KB – 1 MB DRAM
• calculator: no
• channel:
  • selector channel for fast devices
  • multiplexer channel for slow devices

Periphery

• backups:
  • 8 x 7.25 MB magnetic disks (replaceable)
  • hard disk (HDD) 1.6 MB
  • magnetic tape units
• external (peripheral) devices:
  • control console
  • Hollerith punch card reader and puncher
  • punched tape readers and punches
  • letter chain line printer (132 chpl)
  • 151: up to 40 user terminals, each for
    • alphanumeric (CRT) monitor
    • keyboard

Operation

Operating speed: 30 kips

The BS1000 operating system only had a batch mode, the source program had to be submitted on a punched card, and the operators ran it and then returned the printed results and the error list to the programmer.

The machine stored the compiled binary programs on magnetic disk, then concatenated them into an executable and ran them. The concatenation was done using an overlay technique, when only the current program part of the divided program was in the main memory at the same time, and after its completion, the next program part that became current was replaced.

The BS2000 operating system operated in a time-sharing system: terminal users had to log in with their own passwords, after which they were given their own “time slot”, and the system measured their machine time usage. In their own time slot, each user could use the system resources independently of the others, with an average response time of 2-5 seconds; and they could save their work to the backup storage space allocated to them according to their prior request.

Access to magnetic disks:

• soros SAM (Sequential Acces Method)
• direct PAM (Page Access Method)
• indexelt  ISAM (Inex Sequential Access method)

Access to magnetic tapes:

• continuously from the beginning of the tape (overwrite)
• continuously after last record (attribution)

The machine operated with an exceptionally high average fault-free uptime of 95-97% (MTBF > 15.2 hours, based on two-shift operation per day).

Program set

• operating system:
  • 45: PBS 14, then BS1000 paging system, batch mode
  • 151: BS2000 time-sharing system, interactive mode on virtual machines, handling up to 40 user terminals

• compilers:
  • Fortran IV (for general programming tasks)
  • Cobol (for data processing, with good tape management)
  • PL1 (Programming Language 1)
  • RPG (Report Program Generator)
  • Algol
  • Siemens assembler (for time-critical tasks)
• server programs:
  • database administrators:
    • Golem (for text files)
    • Sesam (for relational databases)
    • UDS (for Codasyl-based files)
  • Sort (for sorting data stored on magnetic tape)
  • Siesta, Metaplan (statistical analysis programs)
  • utility, test and conversion programs to assist operation and maintenance
  • 151: Transdata remote data transmission system

Historical curiosities

The machine's instruction set was essentially the same as the instruction set of the later IBM 360 family. The similarity was no coincidence: both IBM and Siemens' developments can be traced back to licensing agreements with RCA Co. (Radio Corporation of America, USA). RCA later withdrew from computing, but IBM and Siemens made it a success. The models of the 4004 family of machines (16, 26, 35, 45, 55, 151) became Siemens' famous computers in Europe.

The configuration built in SZKI was the first in the country on which — after the installation of the Transdata system — the real-time terminal network operated with high reliability under the BS2000 operating system: in two shifts per day (5 days; 16 hours per day), with an average response time of 2-5 s. However, due to the limited main memory and disk capacity caused by the embargo, when serving many users simultaneously, the response times could increase significantly if programs with high main memory requirements (e.g. matrix inversion, sorting of large data files) were running simultaneously.

According to bad language, a talented employee wrote a good chess program, which bored operators sometimes launched during prime working hours — although it was forbidden in principle — and in such cases, response times increased to 25-30 seconds.

"When it was put into operation, it was the largest computer in the country. The owner's chest swelled with pride, even though the BS1000 operating system only had a batch mode, which rarely brought tears of joy from the eyes of the slave-like programmers. Yet it was an unimaginable joy today when the program's scattered punched card package containing the program was reassembled, or when the package submitted for execution was returned the next day with the 137th card syntactically incorrect, or when the package submitted again after the repair ended with an "index limit exceeded" error message.

In comparison, paradise conditions were created when the BS2000 operating system was finally launched, which – in a time-sharing mode based on virtual storage management – could run several programs quasi-simultaneously. Thus – through the continuously developing local network – interactive program development and database management became possible for programmers sitting in front of terminals, as well as direct data entry from remote terminals; first via leased and then data-switched (direct) telephone lines.

Of course, there is no joy without a wormwood: the programmers were fed up, demanding an increasingly insatiable amount of machine time to write, type in and run their ever-larger programs. But the machine's resources proved to be finite, compared to the programmers' time, which they could use for various useful activities during the increasingly long response times – for example, annoying the operators. Until the decision was made: the machine capacity must be expanded. But that's another story.”

(Recollections of Tibor Németi, Deputy Head of the Computer Center)

Resources

The machine's structure, operation, and use are described in detail in the Siemens 4004/45 document, compiled based on the recollections of former programmers.