RPCEmu User Manual

RPCEmu is a emulator of Acorn's Risc PC and A7000 machines. It is a work in progress and should be considered of Alpha Quality.



Most PCs made in the last 5 years should be able to deliver performance similar to an A7000 or RiscPC 600. The recompiler puts these machines into StrongARM territory.

RPCEmu reports how many millions of instructions are executed per second (MIPS). This figure has been widely misinterpreted in the past, partly due to Acorn giving their machines very optimistic performance figures, and partly due to confusion with the DMIPS figure reported by the Dhrystone benchmark.

It is better to compare RPCEmu and real Acorn hardware running actual applications or benchmarks, instead of comparing RPCEmu's MIPS count with what an ARM6 or ARM7 is theoretically capable of.



Download the .msi installer and double click it. This should install it to the default windows program locations (e.g. C:\Program Files\RPCEmu). This will provide you with Start Menu shortcuts for running the program.

Alternatively download the .zip file and install it to a location of your choice.


The Linux version is provided as source code; as such it must be compiled before use. Please refer to the Linux compile instructions for how to compile.

ROM Images

RPCEmu requires a RISC OS ROM image to work, please refer to these instructions for details on how to acquire them.

The Mouse

RISC OS uses a three-button mouse, if your host machine only has two buttons the right and left buttons are mapped correctly, with the middle 'menu' button accessible via the windows menu key (to the left of right ctrl key).

On Linux hosts pressing both left and right mouse buttons simultaneously will generate a middle button click (depending on X server configuration).

Two-button Mouse Mode is available from the Settings Menu; it swaps the right and middle mouse buttons, allowing the more common RISC OS use of Select and Menu on two-button mouse systems such as laptops.

The Menu

RPCEmu contains a menu to access most of the configurable aspects of the program.

menu on windows

File->Reset - Hard-resets the RiscPC. You will lose all unsaved work. Don't use during an IDE hard disc operation, or your disc image may be corrupted! ('Bad Directory' errors and the like).

File->Exit - Exits RPCEmu.

Disc->Load Disc :0 - Loads a .ADF disc image into floppy drive :0

Disc->Load Disc :1 - Loads a .ADF disc image into floppy drive :1

Settings->Configure... - Opens the configuration window. The options here are :

configure window on windows

Settings->Networking... - Please see the Networking Section for more details.

Settings->Fullscreen mode - Puts RPCEmu into fullscreen mode. Press CTRL+END to return to windowed mode. RPCEmu will attempt to change video mode as RISC OS does, to attempt to match it as closely as possible.

Settings->Reduce CPU Usage - Attempts to reduce the host CPU usage of RPCEmu when RISC OS is idle. Requires at least RISC OS 3.60 and does not take effect until roughly 30 seconds after RISC OS has started and RISC OS is not busy.

Settings->Follow Host Mouse - RPCEmu uses a hack to make the RISC OS mouse pointer follow the native pointer. In many games this does not work, so disable this to turn it off. Disabling this enables 'Capture' mouse mode where the pointer will be constrained within the emulators display, click in the window to capture the mouse, and press CTRl+END to release the mouse.

Settings->Two-button Mouse Mode - Swaps the right and middle mouse buttons, allowing the more common RISC OS use of Select and Menu on two-button mouse systems such as laptops

Settings->CD-ROM - various options for the CD-ROM emulation.

Help->Online Manual - If connected to the internet, this opens a browser window to view this online manual.

Help->Visit Website - If connected to the internet, this opens a browser window to visit the RPCEmu homepage.

Help->About RPCEmu - Displays information about this version of RPCEmu and displays copyright and licensing information.

Using ADF floppy disc images

An ADF disc image is a RAW binary dump of a RISC OS formatted disc. As such it will usually be 800K or 1600K in size. RPCEmu supports up to two floppy disc drives, :0 and :1 with one configured by default :0.

You can select which disc image to use on each drive by using the UI provided on the 'discs' menu. See above.

If you wish to configure two drives in RISC OS, use the following command or use !Configure to add them.

*configure floppies 2

Using HDF hard disc images

Up to two IDE hard disc files can be used (only one if a CD-ROM is used). They are called hd4.hdf and hd5.hdf in the program's working directory. Pre-formatted hard drive files are available from the website.

Once the hard disc image is in place you can copy the boot sequence from floppy, CD-ROM or HostFS. To get RISC OS to boot off hard disc, type the following commands at the command prompt:

*dir adfs::4.$
*opt 4,2
*configure filesystem adfs
*configure drive 4
*configure boot

It is possible (though not recommended) to prepare and format your own hard disc files. If you wish to try this, take note of the following:

Using HostFS

HostFS allows you to use a directory on your host operating system as a RISC OS drive. This allows you to more easily move files between the host OS and RISC OS than either Floppy disc imanges or Hard disc images provides.

HostFS always reads from the hostfs directory. Filetypes are represented as a 3-digit hex number after a comma, or a pair of load/exec addresses.

You can use HostFS as main bootable drive within RISC OS by issuing the following commands:

*configure filesystem hostfs
*configure boot

Using the CD-ROM

RPCEmu provides two methods of accessing CDs from RISC OS: ISO images and direct access to the host's CD-ROM drive.

You may need to configure RISC OS to have a CD-ROM drive. If you use a CD-ROM drive you may only have one HDF hard drive file. Use !Configure or use the following.

*configure cdromdrives 1

Use the settings menu described above to access CDs.


Networking is available on the Linux and Windows platforms, please see the RPCEmu Networking Guide for details.


RPCEmu does not support direct printing from RISC OS (there is no parallel port emulation or pass-through to the host parallel port). So the recommended method of printing is to install PrintPDF, print your documents to PDF files, copy them to your host operating system via HostFS and print them there.

Finding Help and Reporting Bugs

If you have any questions or need help, there is a RPCEmu Mailing List, however please specify the version number to avoid confusion. Your patches, suggestions and even bug reports are gratefully recieved.

Contributions: Matthew Howkins, Peter Howkins, Sarah Walker.