RISC OS, the operating system that powered Acorn Computer's Archimedes computers in the 1980s and 1990s, has been fully released to open source.
The move was welcomed by Raspberry Pi CEO Eben Upton: "RISC OS is a great demonstration of how much performance a well-tuned operating system and user interface can wring out of a platform. Moving to a free open source licence should bring a renewed interest to RISC OS."
The shift to open source will enable the operating system to be used in new environments and markets, according to RISC OS Developments director Andrew Rawnsley. "This move unlocks a lot of opportunities for RISC OS that were previously inaccessible due to former licence restrictions. We look forward to seeing the exciting projects that this makes possible," said Rawnsley.
RISC OS is a great demonstration of how much performance a well-tuned operating system and user interface can wring out of a platform
RISC OS started life as Arthur in 1987 and ran on the first ARM microprocessor, the ARM 2, which powered Acorn Computers' Archimedes 305 and 310 PCs. Acorn had developed its own 32-bit microprocessors to power the new computers, which became the basis for the Acorn Risc Machines or ARM microprocessor.
By 1989, the rough edges had been chipped off Arthur, becoming RISC OS 2 instead.
Written in assembly language, the operating system ran from a ROM chip on the Archimedes main board, enabling fast boot-up times and responsiveness. It also rendered the Archimedes immune from the worst effects of any viruses and other malware. Upgrades, though, meant pulling the chip off the main board and replacing it with a new one.
The graphical user interface, though, was RISC OS's strongest point: fast, sensibly designed and highly responsive; where Windows required two mouse buttons and MacOS one, RISC OS required three, with the middle mouse button used to pull-up context-sensitive menus anywhere on the screen. This made RISC OS fast and navigable to use.
It also featured cooperative multi-tasking well before Windows. One of the key usability features of RISC OS was its clear and consistent user interface, reinforced by a style guide published by Acorn to ensure that software developed across the eco-system - both within Acorn and outside - followed the same broad rules.
Acorn also maintained a suite of Archimedes computers for Microsoft, according to their marketing manager at the time, although there's little evidence that Microsoft paid them much heed.
Acorn closed its workstation business in 1998 after its core UK education market shifted to PCs instead and the losses mounted up. It set-up Element 14 in order to focus on set-top boxes and high-performance digital signal processors, moving its base from Cambridge to Bristol in the process.
ARM was also spun-off and floated on the London Stock Exchange as an independent chip-design company, with the funds raised helping to pay for the restructuring. However, with the value of ARM quickly outweighing the value of ‘continuity Acorn', shareholders were keen to enjoy the value of ARM shares directly.
MSDW Investment Holdings, a subsidiary of investment bank Morgan Stanley Dean Witter, was quick to oblige, offering a swap of two ARM shares for every five held in Acorn. Its £270 million acquisition was completed in June 1999. MSDW quickly sold off the set-top box division to Pace Technology for £200,000. Stan Boland, Acorn's last CEO, was given the option of taking Element 14 off their hands for £1.5 million.
Element 14 quickly scooped up a bundle of venture capital cash - including funding from Herman Hauser's Amadeus Capital Partners - to focus on developing IPTV and DSL products, and was subsequently acquired by Broadcom for £366 million in October 2000, becoming Broadcom's DSL business unit.
RISC OS ended up with Pace Technology. It was licensed to both Castle Technology, which continued to make ARM-based PCs running RISC OS for enthusiasts throughout the 2000s, and RISC OS Ltd, whose technology was subsequently passed to 3QD Developments.
In 2006, Castle Technology offered RISC OS under a partly-free licence, enabling enthusiasts to tinker with it for free, but requiring commercial users to pay royalties to Castle.
The full open-sourcing of RISC OS has been enabled by the acquisition by RISC OS Developments of the RISC OS intellectual property from Castle Technology. Risc OS is now open-sourced under the Apache 2.0 licence with RISC OS Open looking after the operating system.
Between the closure of Acorn and the open-sourcing of RISC OS, parallel projects were effectively run, with RISC OS 6 being looked after by Castle Technology, but with development having stalled for the best part of a decade; and RISC OS 5, which has been maintained by enthusiasts, and which forms the basis for RISC OS Open.
Image above by Richard Butler, RJB Online
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