RISCiX

RISC iX was a Unix-like operating system designed to run on the Acorn Archimedes. Heavily based on 4.3BSD, it was initially completed in 1988 — a year after  Arthur but prior to RISC OS. Its relationship to ARX is unknown.
See more at Wikipedia.org...

<operating system> /risk-icks/ (Or "RISC iX") BSD-based Unix developed by Acorn Computers Ltd. (Cambridge, UK) to run on 32-bit ARM RISC processors.
RISCiX was launched circa 1989 for three production machines - the R140, R260, the discless R225; and other prototypes.
(2003-09-24)