RPCEmu and RISC OS 5 on Windows (Rev #12)

History, RISC OS 5 and software compatibility

Early ARM processors had a combined 26-bit program counter and status register, rather than separate 32-bit program counter and status registers.

For a time processors had both 26-bit and 32-bit modes, with the former being phased out by ARM. In October 2002 RISC OS 5 was released using only the 32-bit mode, required because 26-bit mode processors were no longer available – the last being the StrongARM used in the RiscPC.

Most software written in BBC BASIC has no compatibility issues, and in many cases software written in C merely requires a recompilation of the source code, where available. However, some software is reliant on features specific to 26-bit mode and needs updating before it will work.

Recent developments have made RISC OS 5 available for the RiscPC (StrongARM/ARM610/ARM710) and A7000/A7000+ (ARM7500/ARM7500FE).

A ROM upgrade is available to install on real hardware. The following installation notes will allow you to run RISC OS 5 on an emulated RiscPC, and assumes an installation on the most common user hardware/software installation – x86 hardware and Windows.

These notes are based on testing

• Installation on Windows XP and Windows 7 (Windows 8 has not been tested by the author).
• For the author the use of 0.8.15 follows previous installs of 0.8.9, to 0.8.14 with RISC OS 5 in use from early 2012 to present date.

Installation

1. Download the zip archive of RPCEmu 0.8.15.
2. Extract the contents to a directory of your choice – \Program Files\RPCEmu would echo where the auto-installer based install would place it.
3. Download an IOMD ROM image from RISC OS Open. All files, stable and beta, are available from the ROM images page. The recommended ROM for the RiscPC is IOMD stable, other variants exist to cater for other CPUs, each with a stable (even numbered) and a beta (odd numbered) version – this text assumes a stable IOMD ROM.
4. Copy the file “riscos” from IOMD-Soft.5.22.zip\soft\!Boot\Choices\Boot\PreDesk\!!SoftLoad\riscos into the \Program Files\RPCEmu\roms directory. The other files aren’t needed and can be discarded.
5. Download the ROOL self extracting hard disc. As with the ROM image there are both stable and beta versions available. The recommended file is HardDisc4 (self-extracting) – stable. Copy this file to \Program Files\RPCEmu\hostfs\ as “HardDisc4-util,ffc” take care to keep the ,ffc (comma ffc) ending which will be translated by RPCEmu to produce the metadata filetype for RISC OS.

Note 1: RISC OS 5 beta versions are updated frequently with nightly builds from the CVS but may contain bugs so important data should only be trusted to the stable installs.
Note 2: RPCEmu is deemed alpha quality by its authors, which rather negates any comments about stable installs in note 1. In practice, many people use RPCEmu without issue.
Note 3: If you choose to use a beta ROM it is best to use the matching beta HardDisc4 as changes in the ROM may require specific disc based components.

Configuration

1. Double-click \Program Files\RPCemu\RPCEmu-Recompiler.exe to launch it.
2. Ignore the TaskManager error and click on Settings and then Configure.
3. Select the RiscPC StrongARM hardware option, select 128MB or more RAM, and 2MB VRAM.
4. After the restart the emulator will stop at a * prompt. This is because the system is not currently configured correctly to boot into the desktop – type desktop to start the desktop GUI. Cancel the error ‘Machine startup has not completed’.
5. Click HostFS, on the iconbar, to open the root directory.
6. Double-click on the HardDisc4-util to extract the HardDisc4 contents. Wait a while. Double-click the HardDisc4 directory that has been created to open it. Cancel the error ‘No Boot application has been run’, and hold shift down while dragging the !Boot to HostFS:$ (this moves it rather than copying).
7. Press f12 and issue the following commands
   Configure FileSystem hostfs
   Configure Boot
   
8. Press enter twice to return to the desktop then press ctrl-shift-f12 to shutdown.
9. Click the Windows Close button.
10. Double-click \Program Files\RPCemu\RPCEmu-Recompiler.exe to re-launch RPCEmu.
11. When \Program Files\RPCemu\RPCEmu-Recompiler.exe is launched, RPCEmu should now boot to the desktop. All further configuration of RISC OS is personal preference. Access the configuration section of RISC OS by a single click of the Menu (middle) mouse button over the cog icon on the far right of the iconbar.

Networking

Details when I get a reproducible working install.

Limitations

• The emulator does not support IDE harddiscs or CDROM. The OS does, but the emulator has a data loss bug.
• The emulator must be run using the ‘StrongARM’ hardware model, otherwise you will get a lock up during the RISC OS boot sequence.
• If you do not configure the emulator to use 2MB VRAM, you will get redraw issues in the RISC OS desktop.
• The Windows version sometimes exhibits redraw issues – notable if the RPCEmu window overlaps the Windows taskbar.
• The Restart button, on the Shutdown window, should be avoided, because it seems not to reset everything.
• As stated at the top: RISC OS 5 uses the processor in 32 bit mode. There is no provision for mixing 26-bit mode and 32-bit mode applications on the same machine – legacy applications will first need updating.