Acorns's Operating Systems


This page attempts to document the different Operating Systems used by Acorn computers from the most common (e.g. BBC MOS or RISC OS) to the most obscure (ARX or Brazil). if I have missed an OS or version please let me know.

Here are more details of RISC OS versions .

ABC OStbdROM for Acorn Business Computers I/O processor.
Acorn DOSn/aROMSystem 2, 3, 4 & 5ROM was built for specific system configuration
Arthur0.20EPROMArchimedes, very early A300srapidly replaced by 0.30
Arthur0.30ROMArchimedes, early A300supgraded to 1.20
Arthur1.20ROMArchimedes, A300s and A440sreplaced by RISC OS 2.00
Note Arthur ROMs marked 1.10 are actually 1.20
ARXn/an/aArchimedesDeveloped in Acorn's Palo Alto Research Centre for the Archimedes, not completed in time, replaced by Arthur
BraziltbdROMARM second processors and Springboard PC card.OS kernel supporting calls to I/O processor (BBC micro or PC).
CP/M2.2DiscZ80 2nd processor
ABC 1x0
Licensed from Digital Research
DRDOStbdDisc80186 Co-Processorwith GEM
Licensed from Digital Research
Electron OS1.0ROMElectron 
Flex9tbdDiscSystem 3 with 6809 CPU 
Galilleotbd? Set top box OS, never completed 
MOS0.10ROMEarly BBCs up to Issue 4Cassette Filing System only, lots of bits unimplemented.
MOS1.00EPROMEarly BBCsSupported discs drives
MOS1.10ROMUS BBCHas support for NSTC tevelsions and some minor graphics changes
MOS1.20ROMBBCupgrade for MOS 0.1 & 1.0, Used in most BBC Micros
MOS3.50ROMMasterUpgrade only, not fitted as standard
MOS4.00ROMMaster ET 
MOS5.10ROMMaster Compact 
MS-DOS3.00Disc available with PC Emulator .
Licensed from Microsoft
NCOS1.xxROMSet top boxes and NCsbased on RISC OS 3.6
PandoratbdROM32016 2nd processor
Acorn Cambridge Workstation
Panos kernel
more information
Panos1.xDisc 32016 2nd processor
Cambridge Co-Processor
Acorn Cambridge Workstation
more information
PC DOS7DiscRisc PC PCardsLicensed from IBM
RISC iX1.1xDiscR140Acorn's Unix (BSD variant)
more information
RISC iX1.2xDiscR225, R260Acorn's Unix (BSD variant)
more information
RISC OS2.00ROMArchimedes A300s, A400/1, A3000Also available as an upgrade from Arthur 1.20 for older Archimedes
RISC OS2.01ROMR140, R225, R260RISC OS variant to boot RISC iX
RISC OS3.00ROMA5000Buggy release rapidly replaced by v3.10
RISC OS3.1xROMA4, A3010, A3020, A4000, A5000Standard release until the RiscPC launch.
Upgrade from previous versions available.
RISC OS3.50ROMRiscPC600Early RiscPC.s
RISC OS3.60ROMRiscPC600, RiscPC700 & A7000pre StrongARM RiscPCs
RISC OS3.7xROMStrongARM RiscPCs & A7000+Available as an upgrade with StorngARM CPU card
RISC OS3.80DiscDevelopement version for Phoebe
(RiscPC 2)
only released to developers
RISC OS4.0xROMRiscPCs, A7000+, Kinetic RiscPCs, Microdigital Omega and RiscStation R7500.Completed version of RISC OS 3.80 from RISCOS Ltd. Also available as an upgrade to older RiscPCs and A7000s
RISC OS4.05ROMRiscPCs, A7000+, Kinetic RiscPCs etcSupport for interlaced screens in PAL & NTSC on Risc PCs and A7000+s. Includes fixes previously available as ROM patches. Upgrade from RISC OS 3.7 (and 4.02), primarily for users of Millipede Professional Graphics systems.
RISC OS4.xx SelectdiscRiscPCs, A7000+, Kinetic RiscPCs etcSoftloads on top of RISC OS 4.0x. Only available to subscribers to RISCOS Ltd Select scheme
RISC OS4.39 AdjustROMRiscPCs, A7000+, Kinetic RiscPCs etcUpdate to RISC OS 4.0x
Adjust32 is 32bit version for A9home
RISC OS5.xxROMIyonix32bit version for Castle Iyonix
RISC OS6.xxdiscRiscPCs, A7000+Select 4 & 5
softload version from RISC OS Ltd.
Taostbdn/a Being investigated by Acorn mid-1990s. never released