Acorn  Acorn A540
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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.

Source WikiPedia

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.


ARM, an acronym for Advanced RISC Machines (originally Acorn RISC Machines) is a Reduced Instruction Set Computer (RISC) cpu architecture. The ARM1, uses a 32-bit internal structure, but only had a 26-bit address space, limiting the processor to 64MByte of memory. This limit was removed in the ARMv3 series, which introduced a full 32-bit address space.

The first machine that used the ARM chip was the BBC Micro, it used the ARM as a secondary processor at 6MHz.

The result of the simulations on the ARM1 boards led to the late 1986 introduction of the ARM2 design running at 8 MHz, and the early 1987 speed-bumped version at 10 to 12 MHz. The ARM2 was roughly seven times the performance of a typical 7 MHz 68000-based system and twice as fast as an Intel 80386 running at 16 MHz.

The ARM2 featured a 32-bit data bus, 26-bit address space and 27 32-bit registers, of which 16 are accessible at any one time (including the Program Counter). The ARM2 had a transistor count of just 30,000, compared to Motorola's 68000 model with around 68,000. This simplicity enabled the ARM2 to have low power consumption, yet offer better performance than the Intel 80286.

A successor, ARM3, was produced with a 4 KB cache, which further improved performance. The address bus was extended to 32 bits in the ARM3.

source: WikiPedia
Technical Details
Released 1990 Brand Acorn Computers Ltd. Type Acorn Workstations Name Acorn A540 CPU Class ARM CPU ARM3 @26MHz Memory RAM: 4MB
RAM max: 16MB
Sound Chip Integrated Sound 8 channel, 8-bit stereo sound. Display Chip VIDC1A Video Display Processor Display 640x256, 256 colors
640x512, 16 colors
1024x1024, mono
Best Color 256 Colors Best Graphics 1280x1024 monochrome Sprites 1 hardware sprite System OS RISC OS 2 Storage Internal 800K 3.5" Floppy Disk Drive, 100MB Hard Drive
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