cpcec-gtk

Credits

Code — NoRecess
Engine — CPCEC, by Cesar Nicolas-Gonzalez

Credits as they appear in the release.

Note: cpcec-gtk is an abandoned project. It is no longer developed, and no support comes with it. What follows describes it as it was left, in 2022.

cpcec-gtk is an Amstrad CPC, Plus and GX-4000 emulator for Debian-based Linux — Debian, Ubuntu, Pop!_OS and their relatives. The emulation itself is CPCEC, the accurate core written in C by César “cngsoft” Nicolás-González and published under the GPL v3; everything around it — the GTK3 interface, the debugging windows, the packaging and the documentation — is mine, written between 2021 and 2022 on top of the January 2022 build of that core. The whole project, the core included, is on Bitbucket.

It exists for one reason: to have, on Linux, an emulator a CPC programmer can work inside rather than beside. A file that changes on disc is reloaded and restarted on its own, so a toolchain that rebuilds a .dsk puts the new build on screen without a keystroke; the symbol files rasm produces are read, so the disassembly reads in the names the source used; and the whole debugger opens the moment emulation is paused.

What it does

runs .dsk floppy images, .cpr cartridges for the Plus and the GX-4000, and .sna snapshots, and switches to a Plus machine on its own when a cartridge is inserted
opens a file by drag and drop, from the menu, or out of a software library it indexes recursively and filters by extension or by a few letters of the name
reloads and restarts an inserted file the moment its content changes on disc
drives two disc drives, and creates an empty .dsk from scratch
manages the internal ROMs, lower and upper 0 to 127, listing the BASIC RSXs each one carries and letting them be reordered
reads the symbol files rasm writes, both label symbols (-sz) and ROM labels (-er)
takes external game controllers, plugged or unplugged while it runs, and offers a virtual joystick on the arrow keys for anyone without one — with the key-override behaviour of a real Amstrad keyboard
answers ALT+0..9 for the numeric keypad a laptop does not have, and ALT for the Amstrad COPY key
zooms the window, holds a 1:1 pixel ratio, and can show the parts of the CRT monitor a program means to keep out of sight
saves screenshots as .png and snapshots as .sna, mutes, pauses, and runs at 1x or 4x
keeps window positions, library path, last files and mute setting in ~/.config/cpcec-gtk/config.ini

Every emulated machine starts with a 512 KB memory expansion, except the GX-4000, which gets the 64 KB it shipped with.

The debugger

Pausing the emulation opens the debugging windows; esc closes them all and carries on, space steps one Z80 instruction. The Z80 window shows the disassembly, the registers and the stack, takes breakpoints on B, resets the NOP counter on T, disassembles from any address asked of it, and understands the ED FF opcode as a breakpoint written into the code itself. The memory inspector reads the memory as it stands, switches between READ and WRITE values, and reports the Gate Array and ASIC configuration underneath — with the ROM labels when a symbol file supplied them.

The video display window is for racing the beam: it gives the current mode and video memory address, and its CRTC line and monitor scanline fields are interactive — type a value, press the arrow beside it, and emulation runs on until that line is reached. On a Plus or a GX-4000 an ASIC window lists the registers, with sprite previews and bit descriptions in the tooltips. The memory visualiser draws one pixel per byte of the main 64 KB and the first four banks, refreshed at every VSync, in MODE 0 or 1 and in the program’s own palette or in grey — and a last write fading mode shows only the writes, the older frames fading to black.

Screenshots

The main window: the emulated screen, the toolbar and the machine menu — The main window, with the toolbar and the machine menu.

The library window, listing the software found under a chosen folder with its filters — The library: everything found under one folder, filtered by extension or by name.

The ROM configuration window, listing the lower and upper ROMs and the RSXs they carry — ROM configuration, with the BASIC RSXs each ROM brings.

The Z80 debugger, showing the disassembly, the registers and the stack — The Z80 debugger: disassembly, registers and stack.

The memory inspector, showing memory values and the current ROM and RAM configuration — The memory inspector, and the ROM/RAM configuration under it.

The video display window, showing the current mode, the video memory address and the scanline fields — The video display window, for work done against the beam.

The ASIC window, listing the registers of an Amstrad Plus — The ASIC registers, on a Plus or a GX-4000.

The memory visualiser, drawing the contents of memory as one pixel per byte — The memory visualiser: one pixel per byte, refreshed at every VSync.

The emulated CRT monitor extended to show the parts normally out of sight — The CRT monitor extended past its visible 384 by 270 pixels.

Installing it

sudo apt install libsdl2-2.0-0 libgtk-3-0, then sudo dpkg -i cpcec-gtk.deb; sudo apt purge cpcec-gtk takes it away again. The binary goes to /usr/bin, its resources — the Amstrad ROMs, the documentation — to /usr/share/cpcec-gtk/, and nothing is left anywhere else.