Electrologica X8
 EL X8 on display at Museum Boerhaave in Leiden | |
| Also known as | EL X8 |
|---|---|
| Manufacturer | Electrologica |
| Type | Mainframe computer |
| Release date | 1964 |
| Discontinued | 1968 |
| Operating system | THE multiprogramming system |
| Predecessor | Electrologica X1 |
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
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's implementation of the THE multiprogramming system. 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. [1]
- E.W.Dijkstra, Globale beschrijving van de drijvende arithmetiek van de EL X8, EWD145, 6 December 1965. [2]
- E.W. Dijkstra, "The structure of the 'THE' multiprogramming system", Communications of the ACM 11(5):341–346, 1968. Dijkstra's manuscript EWD196 Full text (subscription)
External links
Media related to Electrologica X8 at Wikimedia Commons- The Electrologica X1 and X8 computers
