The EL-X8 computer

Dick Grune

The EL-X8 Simulator X8S

The EL-X8 simulator X8S, written in Algol 60 at the Mathematisch Centrum in Amsterdam, allowed testing of EL-X8 assembly programs during normal operation hours.

The program X8S simulates machine instructions of the EL- X8; it was written entirely in Algol 60, without using special code procedures. The full instruction set of the CPU of the EL-X8 has been implemented, including memory protection and control state. The only component of the input/output processor CHARON that was implemented is the IP facility. The actions and reactions of the simulator during a run (tracing, unusual situations, etc.) are controlled by a Master program, written in a simple control language.

The zip file contains three programs:

1. The X8 simulator X8S in Algol 60 in two versions: one with underlined reserved words (X8S.a60u), and one with reserved words between single quotes (X8S.a60a).

2. The accompanying Master program X8Sm.71.cdl, to be called by the tracing-facility of X8S.

3. A machine-code program in ELAN, both for examining the EL-X8 computer and for testing the EL-X8 simulator X8S.

The Master program can be called from many places in the simulator program, and its first task is finding out what is going on. This requires a sequence of tests, similar to those in a parser. This being part of a compiler construction project, the Master program was written in CDL, the `Compiler Description Language' designed by Kees Koster.

The CDL processor supplied the Algol 60 code for the if-then-else-if-then structure, and the Algol 60 code for the actions was defined by macros. The CDL processor produced (compressed) Algol 60. The Algol 60 code produced by the CDL processor from the Master-program X8Sm.71.cdl can be seen in the program X8S, starting from line 449.

The simulator was described (in Dutch) in Beschrijving van de XS-simulator X8S (1972).

The EL-X8 Manual

The EL-X8 Manual (in Dutch) is available as 240 jpegs of about 4Mb each, and is too large to fit on my Web site. Email me and I'll send you a zip file (850 Mb). For a sample page click here.

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