ARX (operating system)

Infobox OS
name = ARX



caption =
developer = Acorn Computers Ltd
source_model =
kernel_type = Microkernel
supported_platforms = ARM
ui =
family = Unix-like
released =
latest_release_version =
latest_release_date =
latest_test_version =
latest_test_date =
marketing_target =
programmed_in = Modula-2
prog_language =
language =
updatemodel =
package_manager =
working_state = Historic
license =
website =

ARX was a Unix-like operating system written in Modula-2 developed by Acorn Computers Ltd in the UK and at the Acorn Research Centre (ARC) at Palo Alto for their new ARM RISC processors. For the project, Acorn developed its own Modula-2 compiler, Acorn Extended Modula-2 (AEM2), but this was never released externally.

ARX was a pre-emptive multitasking, multithreading, multi-user operating system. Much of the OS ran in user mode and as a result suffered performance problems due to switches into kernel mode to perform mutexes, which led to the introduction of the SWP instruction to the instruction set of the ARM3 version of the ARM processor. This suggests that ARX had a microkernel-type design.

It was not finished in time to be fitted to the Archimedes range of computers, which shipped in 1987 with the Arthur operating system, derived from the earlier MOS operating system from Acorn's earlier 8-bit BBC Micro range. Arthur was later superseded by RISC OS.

Later, a port of 4.3BSD was released, named RISC iX. It had no relationship to ARX.

The Acorn Research Centre was bought out by Olivetti.

External links

* [http://www.chiark.greenend.org.uk/~theom/riscos/docs/Modula2ARX.txt A Usenet post to comp.sys.acorn by Bruce Cockburn detailing the relationship between ARX and Modula-2]
* [http://neil.franklin.ch/Usenet/alt.folklore.computers/20010824_Not_A_RISC_By_Thursday A collection of Usenet posts detailing why ARX was abandoned for RISC OS]
* [http://www.chiark.greenend.org.uk/~theom/riscos/docs/ultimate/a252swp.txt History of the addition of the SWP instruction to the ARM3 instruction set]