This repository hosts a feature-rich fork of RPCEmu, the open-source emulator for Acorn Risc PC and A7000 machines. Alongside the standard emulator core, this edition layers in a modern Qt 5 front-end, a live machine inspector, integrated debugger controls, and a multi-machine configuration system. The project remains distributed under the GNU GPL v2.
- Multi-machine configuration – Create, edit, clone and manage multiple machine configurations from a startup selector dialog. Each machine has isolated CMOS, HostFS and hard disc storage.
- Quick machine switching – Switch between machines on-the-fly via File → Recent Machines without restarting the emulator.
- Shared HostFS drive – A second "Shared" drive icon on the RISC OS icon bar provides access to a common
shared/folder visible to all machine instances, enabling easy file sharing between configurations. - Access/ShareFS networking – Full support for Acorn Access and ShareFS file sharing via NAT networking.
- FPA emulation – Full Floating Point Accelerator (FPA10) coprocessor emulation with all operations implemented and cycle-accurate timing. Enables floating-point intensive RISC OS applications to run correctly.
- Pixel Perfect scaling – Optional integer scaling mode for sharp, crisp pixels without bilinear blur. Toggle via Settings → Pixel Perfect.
- Built-in VNC server – Remote desktop access to RISC OS from any VNC client. Enable via Settings → VNC Server. Connect from tablets, phones, or other computers on your network.
- Sound mute toggle – Quickly mute/unmute audio via Settings → Mute Sound or press F10.
- Machine Inspector window – Inspect CPU registers, pipeline state, MMU flags, performance counters, and key peripheral snapshots (VIDC, SuperIO, IDE, podules) with optional auto-refresh.
- Integrated debugger – Pause/resume execution, single-step (×1/×5), and manage breakpoints and watchpoints directly in the GUI, with clear status readouts for the last halt reason.
- Keyboard shortcuts – Comprehensive keyboard shortcuts for common operations (see Keyboard Shortcuts section).
- Recent disc images – Quick access to recently used floppy and CD-ROM images via the Disc menu.
- Dynarec-aware instrumentation – The ARM dynamic recompiler honours debugger pause requests, breakpoints, and watchpoints via shared hooks (
debugger_requires_instruction_hook) so that interpreter and dynarec stays in sync. - Snapshot plumbing – Thread-safe
MachineSnapshotand peripheral snapshot structs marshal detailed state off the emulator thread for UI consumption without stalls.
The emulator now supports multiple isolated machine configurations:
| Directory | Purpose |
|---|---|
configs/ |
Machine configuration files (.cfg). Each file defines model, RAM, VRAM, ROM, refresh rate, and networking settings. |
machines/<name>/ |
Per-machine runtime data: cmos.ram, hostfs/, hd4.hdf, hd5.hdf. Fully isolated between configurations. |
shared/ |
Common shared folder accessible from all machine instances via the Shared drive icon. |
roms/ |
Shared ROM images. Select which ROM to use per-machine in the Edit dialog. |
Each machine configuration supports:
- Model – RiscPC ARM610/710/810/StrongARM, A7000, A7000+, Phoebe
- RAM – 4 MB to 256 MB
- VRAM – None or 2 MB
- ROM – Select from available ROM files in the
roms/directory - Refresh rate – 20 Hz to 100 Hz (slider control)
- Networking – Off, NAT, Ethernet Bridging, IP Tunnelling (Linux)
- Hard discs – Create/manage HardDisc 4 and HardDisc 5 images (256 MB to 2 GB)
| Path | Purpose |
|---|---|
src/ |
Core emulator engine (ARM interpreter, dynarec, hardware devices, debugger plumbing). |
src/qt5/ |
Qt 5 GUI, machine inspector, debugger controls, configuration selector & networking dialogs. |
slirp/ |
Bundled SLiRP networking library for NAT mode. |
riscos-progs/ |
RISC OS module source code (HostFS, HostFSFiler, ScrollWheel, EtherRPCEm). |
poduleroms/ |
Compiled podule ROM images loaded by the emulator. |
hostfs/ |
Default HostFS content (legacy location, now per-machine in machines/<name>/hostfs/). |
shared/ |
Common shared folder accessible from all RISC OS instances. |
roms/ |
Place your licensed RISC OS ROM images here (see official instructions). |
configs/ |
Machine configuration files. |
machines/ |
Per-machine data directories (auto-created). |
The emulator provides two filing system icons on the RISC OS icon bar:
| Icon | RISC OS Path | Host Path | Purpose |
|---|---|---|---|
| HostFS | HostFS::HostFS.$ |
machines/<name>/hostfs/ |
Per-machine storage, isolated between configurations. |
| Shared | HostFS::Shared.$ |
shared/ |
Common storage visible to all machine instances. |
This allows you to:
- Keep machine-specific files (applications, settings) isolated in each machine's HostFS
- Share common files, utilities, or applications between all machines via the Shared drive
- Transfer files between different machine configurations without network setup
- On startup, the Machine Selector dialog appears listing all available configurations.
- New – Create a new machine configuration with default settings.
- Edit – Modify machine settings (model, RAM, ROM, networking, hard discs).
- Clone – Duplicate an existing configuration.
- Delete – Remove a configuration and optionally its associated data.
- Start – Launch the emulator with the selected configuration.
- Open Debug → Machine Inspector… to reveal the inspector window.
- Tabs provide:
- CPU – Registers R0–R15, CPSR/mode, performance counters, interpreter vs dynarec state.
- Pipeline – Upcoming instruction addresses and opcodes for easy tracing.
- Peripherals – VIDC palette & doublescan mode, SuperIO registers, IDE channel state, podule IRQ mapping.
- Debugger – Run/Pause, Step, Step ×5 buttons, breakpoint & watchpoint lists, last hit summaries.
- Auto-refresh every 500 ms keeps the view current; toggle it or hit Refresh now for manual polling.
- Breakpoints and watchpoints entered in the inspector apply even while the dynarec is active, thanks to the shared debugger hooks in
ArmDynarec.c.
- Qt front-end reworked for stability with modern Qt 5 deployments.
- Multi-machine configuration system with isolated per-machine storage.
- Quick machine switching via Recent Machines menu.
- ROM selection per configuration.
- Dual HostFS drives – Per-machine HostFS plus a common Shared drive for cross-machine file sharing.
- Access/ShareFS networking support for file sharing between emulated machines.
- Full FPA emulation – Complete FPA10 floating-point coprocessor with all operations and cycle timing (see below).
- Pixel Perfect scaling – Integer scaling option for sharp pixels without blur.
- Built-in VNC server – Remote desktop access using libvncserver (Linux). Enable via Settings → VNC Server.
- Sound mute toggle – Quickly mute/unmute emulator audio.
- Recent disc images – Quick access menus for recently used floppy and CD-ROM images.
- Floppy eject actions – Eject floppy discs via menu or keyboard shortcuts.
- In-depth machine inspector and debugger tooling not present upstream.
- Comprehensive keyboard shortcuts for all major functions.
- Dynarec pause logic patched so debugger operations are consistent across cores.
- Custom ARM cross-assembler toolchain support for building RISC OS modules.
| Shortcut | Action |
|---|---|
| Ctrl+S | Save screenshot |
| Ctrl+R | Reset machine |
| Ctrl+Q | Quit emulator |
| Ctrl+1 | Load floppy disc into drive :0 |
| Ctrl+2 | Load floppy disc into drive :1 |
| Ctrl+Shift+1 | Eject floppy from drive :0 |
| Ctrl+Shift+2 | Eject floppy from drive :1 |
| Ctrl+, | Open Settings/Configure dialog |
| F10 | Toggle sound mute |
| F11 | Toggle full-screen mode |
| F5 | Run (resume emulation) |
| F6 | Pause emulation |
| F7 | Single step |
| F8 | Step ×5 |
| Ctrl+I | Open Machine Inspector |
| F1 | Open online manual |
This fork includes complete FPA10 coprocessor emulation, enabling RISC OS applications that use hardware floating-point to run correctly. The implementation includes:
| Category | Operations |
|---|---|
| Dyadic | ADF, MUF, SUF, RSF, DVF, RDF, POW, RPW, RMF, FML, FDV, FRD, POL |
| Monadic | MVF, MNF, ABS, RND, SQT, LOG, LGN, EXP, SIN, COS, TAN, ASN, ACS, ATN, URD, NRM |
| Conversion | FIX (float→int), FLT (int→float) with all IEEE rounding modes |
| Comparison | CMF, CMFE, CNF, CNFE with proper NaN exception handling |
| Transfer | LDF, STF, LFM, SFM (load/store single and multiple) |
- Cycle-accurate timing – Each operation has appropriate cycle costs (e.g., 10 cycles for load/store, 150 cycles for transcendental functions like SIN/COS/TAN).
- IEEE rounding modes – FIX, RND, and URD support all four IEEE 754 rounding modes (nearest, +∞, −∞, zero).
- NaN handling – Comparison operations correctly set the V flag for unordered (NaN) comparisons.
- Dynarec integration – FPA works with both the interpreter and dynamic recompiler.
- Ensure 16-bit sound is enabled in RISC OS configuration for correct audio playback when using FPA-intensive applications.
- Some applications (e.g., !AMPlayer) may exhibit timing-sensitive behaviour; if issues occur, test with the interpreter mode.
| Symptom | Remedy |
|---|---|
| Emulator launches without a window | Ensure Qt 5 runtime libs are discoverable; this fork delays snapshot requests to avoid deadlock, so missing Qt plugins are the usual culprit. |
| No network connectivity | Confirm SLiRP support was compiled in (CONFIG_SLIRP) and NAT rules are configured. |
| ROM not found | Ensure ROM files are placed in the roms/ directory and selected in the machine configuration. |
| Machine data not persisting | Check that the machines/<name>/ directory exists and is writable. |
Issues and pull requests are welcome, especially around debugger/inspector features.
- Licensed under the GNU General Public License v2. See
COPYINGfor details. - Original emulator by the RPCEmu contributors.