RISC OS Timeline


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This is meant to be a complete history of Acorn Computers, RISC OS development with particular detail on post-Acorn events

The events surrounding development of RISC OS beyond its last release by Acorn (version 3.7) have become contentious in the RISC OS world, usually as a result of those trying to rewrite history to their own ends. This details hopefully the most accurate version of those events to date, and will serve as a future reference.

Much of this timeline is based directly on information provided by Steve Revill (a former Acorn employee) and Peter Howkins (who maintains a database of RISC OS version information). It was compiled by Peter Naulls and has then been extended by James Scholes and others.


Early Acorn


  • 5/12/1978 – Acorn Computers established in Cambridge, England as a trading name of Cambridge Processor Unit Ltd.


  • 03/1980 – Acorn Atom launched.



  • 12/08/1981 – IBM PC launched
  • 2/1986 – BBC Master launched

Archimedes Era

RiscPC Era


  • 04/1994 – RiscPC launched


  • NCOS is merged back into CVS both before and during RISC OS 3.80 development.
  • 25/08/1998 – Acorn Release RISC OS 3.8 to registered developers. 3.80, codenamed Ursula is the 'beta' for the version of RISC OS that will appear in the RiscPC2 (Phoebe). It has been deliberately nobbled to only run on ARM 6 and ARM 7 machines to discourage developers from keeping their SA RiscPC and 3.80 once the RiscPC2 is released. RISC OS 3.80 has some bugs, but generally shows about 90% of the content/work of RISC OS 4.02. A SA capable ROM image was made available to a few people as well, and likely used in-house at Acorn.

Post Acorn


  • 17/09/1998 – Acorn closes the workstation division, ceases development on Phoebe. RISC OS development continues as a black project amongst a few engineers, leading to the various revisions of Ursula ROM softload patches for RiscPC.


  • 15/01/1999 – The remaining parts of Acorn rename as Element 14 Ltd.
  • 05/03/1999 – RISCOS Ltd secure the rights to develop RISC OS for the desktop market and receive source code from Element 14. This was probably the latest version to date, and includes some early 32-bit and HAL work.
  • 27/04/1999 – The breakup of Element 14 Ltd to free up its ARM shares. The bank MSDW purchase the shares of Element 14, then sell the silicon design buisness to Stan Boland and the management team for £1.5 million. The STB business went to Pace for £200,000. These changes are finalised by 03/06/1999.
  • 01/07/1999 – RISCOS Ltd, having completed RISC OS code to a sellable state, release RISC OS 4.02 for sale to the general public.
  • 09/1999 (or so) – drobe.co.uk launches


  • 10/2000 – Element 14, the silicon design business, is sold to Broadcom in a stock deal worth approx $594 million (USD).
  • 08/08/2000–02/04/2001 – Pace Engineers continue to build soft-loadable versions of RISC OS for RiscPCs including the 32-bit/HAL work. These are considerably more polished than 3.80, and appear to be as feature complete as ROL's 4.02. Some code from RISC OS 4.02 is included from ROL (who is now selling Select).



  • 04/07/2003 – Castle purchase RISC OS from Pace.


  • 09/07/2006 – RISC OS Open is announced following two weeks of speculation after the company registration was spotted on Drobe. It shortly emerges that it is a project to offer the source to several parts of RISC OS for open modification.


  • 30/04/2007 (estimate) – After several soft-loadable releases, RISCOS Ltd release RISC OS 6 "the 32 bit neutral version of RISC OS developed by RISCOS Ltd."
  • 19/05/2007 – Castle and RISC OS Open release their first sources.



  • 21/09/2009 – drobe.co.uk shuts down into archive mode after 10 years.
  • 22/09/2009 – riscos.info starts covering RISC OS news.

See Also

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