Electrologica X1

The X1 computing machine, was the first machine built by Electrologica N.V.. In total an amount of 40 X1 machines are sold. In 1956 specifications of this machine were finished and at the end of 1957, the first prototype was available. The X1 became a success because of its general applications of use in calculations.

Technical Implementation

Electrologica X1 computer, around 1960

Electrologica X1 computer, around 1960.

The X1 used semiconductor logic and consisted only of germanium transistors as switches, which reduced the amount of power consumption of the X1 machine. Because of the relative low power consumption, a couple of hundreds of Watts, cooling systems became superfluous. Another great revolution was the use of magnetic core memory units which were accessible in parallel. The memory units consisted of 27 bits and a maximum amount of 32768 words. An amount of 8192 words were read-only, which were implemented with fixed connections, which reduces costs.

The X1 made use of decimal input and output mechanisms, but internally it worked binary, like the ARMAC. This was also the first machine using interrupts, which increased I/O performance. The machine generated an interrupt when input or output were available. The interrupt idea is published by E.W. Dijkstra in his Ph.D. Thesis: "Communition with an Automatic Computer". This mechanism achieves asynchronous I/O handling, which ensures that the system did not have to wait for relative slow terminal devices.

Also an ALGOL 60 compiler became available for the X1 machine, which was written at the Mathematical Center in a couple of months time. This compiler was written by Edsger Dijkstra and Jaap Zonneveld and was the first running ALGOL 60 implementation in the world. The run-time system for the X1 was written by Marlene Römgens and Fiek Christen. Recently, prof. F.E.J. Kruseman Aretz, professor emeritus from Eindhoven University of Technology, has completely reverse engineered and documented the compiler from Dijkstra's original hand-written notes. A report can be obtained from the CWI repository[1].

One of the success stories of the X1 is the fast availability of an ALGOL60 compiler, written at the Mathematical Center.


To get an idea of the duration of a computation in those years, it may be illustrative to mention some timings for the X1:

  • Addition of two numbers took place in around 64 micro seconds.
  • Addition of two floating point numbers took place in around 96 to 108 micro seconds.
  • Multiplication of two numbers took place in around 500 micro seconds.
  • Multiplication of two floating point numbers took place in around 332 to 612 micro seconds.
  • Division of two numbers only took place in around 62 micro seconds, which is very remarkable.

What is Next?

The successor of the X1 became the Electrologica X8, after some successful years performing computations.


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