The Acorn A540 Archimedes flagship
The Acorn A540 was launched in June of 1990 and considered the flagship of the Archimedes range of computers. The heart of the computer was the ARM3 CPU, and it could be expanded with an FPA10 floating point accelerator. The machine had standard 4Mbyte of RAM which could be expanded to 16Mbyte using additional RAM cards. Those cards had 4Mbyte each, and each card had their own MEMC1a memory controller unit.
Unlike the other Archimedes computers, this machine came with a SCSI expansion module (Podule) and a 100MByte hard drive. The A540 was launched with the RISC OS 2.01.
The A540 hardware was almost identical to the R260 Workstation except that the RISC iX operating system was not installed in ROM. However, it could be purchased separately on disk.
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.
Arthur Operating System
The Acorn Archimedes computers were initially shipped with the Arthur OS, but could be upgraded to RISC OS, by replacing the ROM chips that contained the operating system. Because of these ROMs, the computer would boot immediatly into it's GUI, similar to the Atari ST line of computers. This gave them a significant advantage over PC's that loaded the operating system from disk.
The early Archimedes computers used the Arthur operating system, which was replaced in 1989 with RISC OS. RISC-OS featured co-operative multitasking, task management, solid window manipulation, adaptive rendering of bitmaps and coloring, and above all stability that the Arthur OS lacked. New applications quickly started to take advantage of the RISC-OS resulting in mature software such as Acorn Desktop Publisher, and even a PC Emulator.
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.