Acorn  Acorn R260

The Acorn R260 workstation

The Acorn R260 was a RISC iX workstation, based on the Acorn A540. It was released with an ARM3 processor, running at 26MHz, later to be upgraded to 33MHz. The machine came with 8MByte RAM, a 100MByte SCSI hard drive and booted straight into RISC iX.

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.


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 Country United Kingdom Brand Acorn Computers Ltd. Type Acorn Workstations Name Acorn R260 CPU Class ARM CPU ARM3 @26Hz 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 iX (Unix) Storage 3.5" Internal Disk Drive, 100MByte SCSI Hard Drive
Related Systems
Acorn BBC/Acorn 8-bit
Acorn Archimedes 300/400
Acorn New Archimedes 400s
Acorn Workstations
Acorn  R260 (1990)
Acorn Archimedes 3000+
World Wide Web Links
Acorn Computers
A list of all Acorn machines