The Acorn R225 network workstation
Acorn Archimedes Computers
The Acorn Archimedes computer was the commercially available computer to use the RISC (Reduced Instruction Set CPU) architecture. The first models were launched in 1987, and Acorn developed updated models of the machines until the early 1990's. The CPU in the Acorn machines is the ARM chip, which stands for Acorn RISC Machine. ARM Chips are still used today, one popular example is the iPhone.
RISC iX - Unix for the Archimedes
RISC iX is a Unix operating system designed to run especially on the Acorn Archimedes microcomputer. It was completed in 1988, based on BSD v4.3 and first introduced on the R140 on 1989.
Due to a restriction of the hardware, a 32KByte memory page size, processes that stayed in memory that reequired separate pages, gobbled up memory fast. The system therefore introduced shared library support, and paging of compressed executables, to work around some of these memory management unit restrictions.
The operating system was intended for use on the Acorn R140, the Acorn R225 and the R260. The Acorn A540, being almost idendical to the Acorn R260 could also run RISC iX. In order to run this OS on the older A400 machines, a SCSI card and an upgraded memory controller were needed. The A300 and A3000 series did not support RISX iX.