© Copyright 1997–2015 Ulrich Doewich
© Copyright 2016–2025 Colin Pitrat
© 2026 Cezar "ikari" Pokorski
https://github.com/ikari-pl/konCePCja
konCePCja is a software emulator of the Amstrad CPC 8-bit home computer series, running on Linux, macOS and Windows. It faithfully imitates the CPC464, CPC664 and CPC6128 models, plus the CPC464+, CPC6128+ and GX4000 Plus Range machines. By recreating the operations of all hardware components at a low level, the emulator achieves a high degree of compatibility with original CPC software. Programs and games run unmodified at real-time or higher speeds, depending on the host environment.
konCePCja is designed as an IPC-controllable debugging tool — every feature is accessible via a TCP text protocol, making it scriptable by automation pipelines, CI systems and LLM agents. The 18-window Dear ImGui DevTools UI is built on top of the same API.
konCePCja is a fork of Caprice32 with a WinAPE-class debugger, full IPC automation and a modern Dear ImGui interface. 831 tests across 88 suites.
- SDL3 migration + macOS menu integration
- Dear ImGui overlay with 18 DevTools windows (see DevTools below)
- Dockable workspace — Classic (floating windows) or Docked mode with Debug, IDE and Hardware layout presets, plus custom save/load
- DevTools toolbar — toggleable second topbar (F12) with dropdown menus and step/pause controls
- SDL_Renderer fallback — automatic fallback to software rendering on systems without OpenGL
- Software scanlines — configurable scanline intensity for all video backends (GL and software)
- Auto frameskip — skip rendering when emulation falls behind real-time speed
- High-res speed limiter — nanosecond-precision frame pacing with catch-up after compositor stalls
- Bottom status bar — drive LEDs, tape controls and filenames moved to a dedicated status bar
- PNG logo + macOS icns icon
- IPC protocol — TCP server on port 6543 for remote control by scripts and LLM agents
- Telnet console — persistent TCP text terminal on port 6544, mirrors CPC output and accepts keyboard input (
nc localhost 6544) - Headless mode (
--headless) — run without a window for CI and automation - Input replay — type text, press keys and control joysticks over IPC
- Auto-Type —
autotypecommand with WinAPE~KEY~syntax for scripted keyboard input - Frame stepping — advance exact frame counts for deterministic testing
- Exit control —
--exit-after,--exit-on-breakandquitfor scripted runs - Hash commands — CRC32 of VRAM, memory ranges and registers for CI assertions
- Event system — fire IPC commands on PC match, memory write or VBL interval
- Breakpoints with conditional expressions (
if A > #10 and peek(HL) = #C9) and pass counts - Watchpoints — memory access breakpoints on read, write or both with address ranges
- IO breakpoints — break on Z80 IN/OUT with port masks and conditions
- Step over / step out / step to — function-level stepping, not just single instructions
- Expression parser — WinAPE-compatible syntax with registers,
peek(),ay(),crtc(), bitwise operators - Debug timers — measure T-state durations between code points via expression side-effects
- Z80 Assembler — integrated assembler with labels, expressions,
&/$/%number formats, two-pass assembly, error reporting and IPC access - Symbol table — load/save
.symfiles, bidirectional lookup, symbols in disassembly output - Memory search — find hex patterns (
??wildcards), ASCII text, or Z80 mnemonics (ld (*),hl) - Call stack — heuristic stack walk with CALL/RST detection and symbol labels
- Data areas — mark address ranges as bytes/words/text for correct disassembly output
- Disassembly export — export address ranges to source files with optional symbol labels
- Instruction trace — ring-buffer Z80 execution trace with dump to file
- Memory bank viewer — read through Z80 banking, write path, or raw physical banks
- Disassembly improvements — PC pinned at fixed position, ROM region color-coding, bank boundary markers at 16K boundaries
- Disc file editor —
disk ls/get/put/rmfor AMSDOS files on DSK images - Sector editor — read/write individual sectors by track/side/sector ID
- Disc formatting — create blank discs in standard CPC, IBM, and custom formats
- WAV recording — capture audio output to WAV files
- YM recording — capture PSG register writes to YM chiptune files
- AVI recording — capture video+audio to AVI files
- Frame dumps — save sequential PNG screenshots or animated GIFs with LZW compression
- Full Plus Range — CPC464+/CPC6128+/GX4000 with ASIC hardware sprites, enhanced palette, DMA sound channels, and vectored interrupts
- CRTC type selection — types 0, 1, 2 and 3 with per-type register behaviour
- 4MB RAM expansion (Yarek-compatible) — configurable up to 4096 KB
- Silicon Disc — 256 KB battery-backed RAM disc in banks 4-7
- 32 ROM slots — load/unload/query ROM images
- ASIC register viewer — sprites, DMA channels, palette, interrupts
- Video / Audio state — live CRTC, Gate Array, PSG register viewers with audio oscilloscope
- M4 Board — virtual filesystem with host directory backing, 52 firmware commands, RSX commands, DSK container support, LED status and embedded HTTP server (web file browser, ROM management, CPC control, live video preview — compatible with
cpcxferand M4 Board Android app) - Symbiface II — IDE hard disc (ATA PIO with raw
.imgfiles), DS12887 RTC with NVRAM, PS/2 mouse - Digiblaster — printer port 8-bit DAC mixed into audio output
- AmDrum (Cheetah) — 8-bit DAC on port
&FFxx - Dobbertin SmartWatch — Dallas DS1216 phantom RTC returning host system time
- AMX Mouse — joystick port mouse on keyboard matrix
- Amstrad Magnum Phaser — light gun via CRTC register intercept
- Drive/tape sounds — procedurally generated FDC motor hum, head seek clicks and tape loading hiss
- Session recording — record and replay full emulator input/state sessions
- Graphics finder — decode CPC Mode 0/1/2 pixel data at any address with zoom and paint
- Pokes system — load, apply and manage game cheats in .pok format
- Configuration profiles — save and switch between named config presets
See docs/ipc-protocol.md for the full IPC command reference (80+ commands).
- Complete emulation of CPC464, CPC664 and CPC6128
- Plus Range support: CPC464+/CPC6128+/GX4000 with ASIC sprites, DMA, enhanced palette, and vectored interrupts
- CRTC types 0-3 with per-type behaviour
- Joystick support — fully usable with joystick only, thanks to an integrated virtual keyboard
- Joystick emulation — joystick-only games can be played using the keyboard
- English, French or Spanish keyboards
- DSK, IPF and CT-RAW files for disks — VOC and CDT files for tapes — CPR files for cartridges
- Snapshots (SNA files)
- Direct load of ZIP files
- 18-window ImGui DevTools: registers, disassembly, memory hex, stack, breakpoints, symbols, data areas, graphics finder, session recording, silicon disc, ASIC viewer, disc tools, disasm export, video state, audio state, recording controls, assembler, instruction reference
- Dockable workspace with Debug/IDE/Hardware presets and custom layout save/load
- Disc file editor, sector editor and formatting (IPC and GUI)
- WAV, YM and AVI recording
- Software scanlines with configurable intensity
- SDL_Renderer fallback for systems without OpenGL
- 8 peripheral expansions: M4 Board (with HTTP server), Symbiface II, Digiblaster, AmDrum, SmartWatch, AMX Mouse, Phaser, drive/tape sounds
- Custom disk formats
- Printer support
- Experimental Multiface 2 support (prefer the memory tool where possible)
- 831 unit tests across 88 test suites
Something missing? Open an issue to suggest it.
Press F12 or send devtools via IPC to toggle the DevTools toolbar below the main topbar. The toolbar provides dropdown menus (CPU, Memory, Hardware, Media, Export) and step/pause controls. All 18 windows are also accessible from the command palette:
| Window | Description |
|---|---|
| Registers | Z80 registers and flags, editable in-place |
| Disassembly | Live disassembly with follow-PC, goto address, symbol labels and data area formatting |
| Memory Hex | Hex editor with configurable bytes-per-row and goto address |
| Stack | Stack view with heuristic CALL/RST detection and symbol names |
| Breakpoints | Unified table of breakpoints, watchpoints and IO breakpoints with add/delete forms |
| Symbols | Symbol table with filter, add/delete, load/save .sym files |
| Data Areas | Mark memory ranges as bytes/words/text for correct disassembly |
| Disasm Export | Export disassembly to source files with address range and symbol options |
| Session Recording | Record, stop and replay emulator sessions with progress display |
| Recording Controls | Transport controls for session playback with progress bar |
| Graphics Finder | Decode CPC pixel data at any address in Mode 0/1/2, with zoom, palette selector and paint |
| Silicon Disc | Enable/disable, bank usage display, clear/save/load the 256K RAM disc |
| ASIC Viewer | Plus Range hardware: 16 sprites, 3 DMA channels, 32-colour palette, interrupt state |
| Disc Tools | Drive selector, disc formatting, AMSDOS file browser, sector-level read |
| Video State | Live CRTC and Gate Array register display |
| Audio State | Live PSG (AY-3-8912) register display with oscilloscope |
| Assembler | Z80 assembler with labels, expressions, error list and assemble-to-memory |
| Instruction Reference | Searchable Z80 opcode table (1268 entries across 7 prefix groups) |
In Docked mode, windows snap into a tiled layout. Three presets are available (Debug, IDE, Hardware) and custom layouts can be saved/loaded from the Layout menu.
See INSTALL.md.
git clone --recurse-submodules https://github.com/ikari-pl/konCePCja.git
cd konCePCja
make APP_PATH="$PWD"
./koncepcja
Note: A plain
makewithoutAPP_PATHproduces a debug-oriented build that looks forkoncepcja.cfgin the current working directory, not next to the executable. SetAPP_PATHto get the documented behaviour.
Download a release from https://github.com/ikari-pl/konCePCja/releases, decompress it and run:
./koncepcja
Download a release from https://github.com/ikari-pl/konCePCja/releases, decompress it and double-click koncepcja.exe.
See the manual page for details. If you are lost, launch the emulator without arguments and press F1 for the in-emulator menu.
See INSTALL.md for build instructions.
The source for konCePCja is distributed under the terms of the GNU General Public License version 2 (GPLv2), included in this archive as COPYING.txt.
The screen-capture code uses driedfruit SDL_SavePNG, released under the zlib/libpng license (compatible with GPLv2).
The bundled ROM images in rom/ are © Amstrad plc and Locomotive Software Ltd, redistributed with permission.
Amstrad have kindly given their permission for the redistribution of their copyrighted material but retain that copyright.
See rom/ROM-LICENSE.txt for full details including the Multiface II ROM.
Bug reports, feature suggestions and pull requests are welcome — just open an issue or submit a PR.