The Electrologica X8 (or EL X8) was a digital computer designed as a successor to the
Electrologica X1 and manufactured in the Netherlands by
Electrologica NV between 1964 and 1968.
Like its predecessor, the
X1, the X8 system included
core memory, 27-bit word length, and
drum memory
Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory.
Many early computers, called drum computers or drum machines, used drum ...
as secondary storage (not as primary storage). The memory address was increased from 15 to 18 bits, for a theoretical maximum memory size of 256k words. The X8 included an independent peripheral processor called CHARON (Centraal Hulporgaan Autonome Regeling Overdracht Nevenapparatuur, or Central Coprocessor Autonomous Regulation Transfer Peripherals) which handled I/O. Other features included up to 48 input/output channels designed for low speed devices such as paper tape, plotters and printers. Unlike the X1, the arithmetic unit of the X8 included
floating point arithmetic, with a 41-bit mantissa and 12-bit exponent (which adds up to 53 bits rather than 54; the reason is that there are two copies of the mantissa sign bit).
The system is most notable as the target processor for
Edsger Dijkstra
Edsger Wybe Dijkstra ( ; ; 11 May 1930 – 6 August 2002) was a Dutch computer scientist, programmer, software engineer, mathematician, and science essayist.
Born in Rotterdam in the Netherlands, Dijkstra studied mathematics and physics and the ...
's implementation of the
THE multiprogramming system
The THE multiprogramming system or THE OS was a computer operating system designed by a team led by Edsger W. Dijkstra, described in monographs in 1965-66
(Jun 14, 1965)
and published in 1968.
Dijkstra never named the system; "THE" is simply ...
. This includes the invention of
semaphores, enabled by a specific instruction in the X8 instruction set. Semaphores were used not only as a synchronization mechanism within the THE operating system, but also in the request and response data structures for I/O requests processed by the CHARON coprocessor.
References
* E.W.Dijkstra, ''Documentatie over de communicatie apparatuur aan de EL X8'', EWD140, undated.
* E.W.Dijkstra, ''Globale beschrijving van de drijvende arithmetiek van de EL X8'', EWD145, 6 December 1965
* E.W. Dijkstra, "The structure of the 'THE' multiprogramming system", ''Communications of the ACM'' 11(5):341–346, 1968
Dijkstra's manuscript EWD196Full text (subscription)
External links
*{{Commonscatinline, Electrologica X8
Mainframe computers
Science and technology in the Netherlands
Computer science in the Netherlands
Computers designed in the Netherlands