A 26 bit build of RISC OS

VERY VERY ALPHA, YOUR FILES/SANITY MAY BE AT RISK

This is a Rom Image and hard disc image of RISC OS, built from the open ROOL sources, but compiled up in 26bit compatible mode.

It mostly uses code from approx 2000-2002, compiled up with a set of contempory tools.

It should be compatible with Acorn RiscPCs, A7000s, A7000+, and the emulator RPCEmu.

The source code for this project is available on gitlab.4corn.co.uk, with all the changes committed to the 'twentysix' branch. Please see below for downloading and building instructions.

Latest download

Version 4.00 release C1 - 17/6/2024

Older Versions

Installing on RPCEmu

Download and install/compile RPCEmu as usual.

Download the 'ROM Image', unzip and place in the the roms/ directory.

Download the 'Hard Disc in Emulator HostFS format', unzip and place contents of 'HardDisc4' in the root of the hostfs/ directory.

Run rpcemu-interpreter (recompiler will not function yet), and RISC OS should run, but without booting off the Harddisc.

For best compatibility, edit your RPCEmu config, Settings->Configure, and change the 'Hardware' to 'RiscPC - StrongARM' and click OK, this will reboot RPCEmu.

Enter the command line (F12), and type the following.

*configure filesystem hostfs
*configure boot

Reboot RPCEmu, File->Reset, and it should execute the Boot sequence.

Installing on real machine

Unknown if this softload will load over the top of RISC OS 4.00 ROMs or higher

Download 'ROM Image' and 'Hard Disc in zip Format' and copy them to your hardware. Move asside your existing !Boot, Apps, and other folders, from the root of your machine.

Unzip the contents of 'Hard Disc in zip format' HardDisc4 folder and place in the root of your harddisc.

Unzip the contents of 'ROM Image' and place the file in !Boot.Softload. Rename the rom image file to 'Ursula'

Reboot the machine, it should softload the new OS.

Building from source

Environment


RPCEmu with 3.71 easy-start bundle installed, running under Linux.

Checkout code


 cd rpcemu/hostfs
 git clone https://gitlab.4corn.co.uk/Products/All.git
 cd All
 git submodule update --init --remote --no-fetch

The MIDIPlay module might not checkout, don't worry about it

Change the the 26bit build's branch

 git submodule foreach git checkout twentysix

Install build tools in library


The build requires binary build tools, I'm currently using a set from 2001, other versions may work, but I've not tested them.

In All.RiscOS.Library copy in the following files

  • bison
  • diff
  • flex
  • gawk
  • ident
  • Acorn/aasm
  • Acorn/amu
  • Acorn/c++
  • Acorn/cc
  • Acorn/cfront
  • Acorn/cmhg
  • Acorn/decaof
  • Acorn/libfile
  • Acorn/link
  • Acorn/objasm
  • Acorn/objsize
  • Acorn/resgen
  • Build/truncate

Building ROM


Boot RISC OS

Use task manager and make sure the drag the 'next' slot to have about 8MB

Run All.RiscOS.Apps.!Builder

In the Build directory drop down, make sure your All.RiscOS folder is selected. If not listed, middle click on the !Builder iconbar icon, and use 'Register build tree...'

In the Environment drop down select the 'Ursula' entry.

In 'Build Options' select;

  • List
  • Clean
  • Clean all
  • Export headers
  • Export libraries
  • Export resources
  • Make ROM
  • Install ROM
  • Join ROM

and then click the 'Build' button.

After quite a while the build should finish, and if it has built it a 4MEG ROM image should be in;

All.RiscOS.Images

with a name similar to xUUR00-00

where 'x' is a lower case letter that the builder iterates through the alphabet.

If it failed the build logs are in

All.RiscOS.BuildSys.Logs

with a name similar to xUUR00-00

Build Disc Image


In the Environment drop down select the 'Disc' entry.

In 'Build Options' select;

  • List
  • Clean
  • Clean all
  • Export headers
  • Export libraries
  • Export resources
  • Install disc

and click 'build'

Once built, however, Unselect

  • Clean
  • Clean all
  • Export headers
  • Export libraries
  • Export resources
leaving just
  • List
  • Build disc

and hit 'build' again

This 'double' build of the disc image, is due to not correctly creating all needed directories in the correct order on the first pass. The second run therefore fills in some gaps. Hopefully this can be resolved in a future code change.

Known Issues:

  • Untested on real hardware
  • Not sure it will softload on machines with version 4.00 or higher already installed...
  • On RPCEmu, does not work in recompiler (bug in RPCEmu being investigated)
  • On RPCEmu, works better in StrongARM mode (likely another RPCEmu bug)
  • May be missing modules and harddisc apps people would expect to be there
    • ShareFS missing from ROM
    • Host and GetHost network commands missing from disc
  • Only very lightly tested