Copyright (c) 1999-2025 Jiri Svoboda
GZX is a ZX Spectrum emulator. I wrote it at a time where Linux had no good emulators and it's been the only emulator I used ever since.
Some of the features of this emulator:
- Run in Windows (DirectDraw or GDI), Linux (SDL 1.x), HelenOS
- ZX Spectrum 48K, 128K, +2, +2A
- Joystick (Kempston) emulation
- AY-3-8192
- Read, write and convert TZX, TAP, WAV tape formats
- Z80, SNA, AY snapshots
- Double line mode (i.e. interlaced image emulation)
- ULAplus emulation
- Spec256 (not 100% done)
- Emulate built-in MIDI port of 128K Spectrum
- Record audio to WAV file
- Record data sent to I/O ports
- Built-in debugger
Most of this emulator (i.e., source code, binaries, emulator font FONT.BIN, documentation) is free software, provided under an MIT-style license. The only exception are the enclosed ZX Spectrum ROM files. The copyright to the ROM files was held by Sinclair Research ltd. and later Amstrad plc. Amstrad allowed distributing ZX Spectrum ROM files toghether with emulator software.
In Linux:
$ ./gzx [options]
In Windows:
> gzx.exe [options]
Supported command-line options:
| Option | Description |
|---|---|
| -midi | Output to specified MIDI device |
| Load snapshot file at startup |
Note that most functions can be accessed via menus as well as via shortcuts.
| Key | Function |
|---|---|
| Esc | Open main menu |
| F2 | Save snapshot |
| F3 | Load snapshot |
| F4 | Display options |
| F5 | Tape menu |
| F6 | Hardware options |
| F7 | Reset |
| F8 | Select model |
| F9 | Select tapefile |
| F10 | Quit |
| F11 | Toggle fullscreen mode |
| F12 | Enter debugger |
| Alt-Shift-L | Lock down UI (disable emulator control keys) |
| Alt-Shift-U | Unlock UI (reenable emulator control keys) |
These might change or be removed in the future:
| Key | Function |
|---|---|
| Alt-W | Open Record Audio dialog to start recording audio to WAV |
| Alt-E | Stop recording audio |
| Alt-R | Start recording I/O port output to out.ior |
| Alt-T | Stop recording I/O port output |
| Alt-N | Select previous/none Spec256 background |
| Alt-M | Select next Spec256 background |
On the numerical keypad:
| Key | Function |
|---|
- | Start the tape
- | Stop the tape
- | Rewind the tape / | Toggle quick load
| Key | Spectrum Key |
|---|---|
| Shift | Caps Shift |
| Ctrl | Symbol Shift |
| Caps Lock | Caps Lock |
| Arrows | Arrow Keys |
| Backspace | Delete |
| Backtick | Graph |
| Tab | Extend Mode |
| Insert | Edit |
| Delete | Break |
| Enter | Enter |
| [ | True Video |
| ] | Inverse Video |
| Comma | , |
| Period | . |
| Semicolon | ; |
| Quote (') | " |
| Minus | - |
| Equals | = |
| Key | Function |
|---|---|
| Esc or Enter | Exit debugger, return to normal emulation |
| Tab | Switch focus between dissassembly and hex view |
| Up Arrow | Move cursor to previous instruction / row of memory |
| Down Arrow | Move cursor to next instruction / row of memory |
| Page Up | Move cursor up one page |
| Page Down | Move cursor down one page |
| Home | Move cursor up by 256 bytes |
| End | Move cursor down by 256 bytes |
| F7 | Trace into |
| F8 | Step over |
| F9 | Go to cursor (run until PC = cursor position) |
| F11 | View Spectrum screen (while paused) |
Cursor block keys are mapped to Kempston joystick, as follows:
| Key | Spectrum Key |
|---|---|
| Arrow keys | Direction |
| Insert | Button 1 |
| Delete | Button 2 |
| Home | Button 3 |
Some demos make use of the interlaced nature of PAL image by displaying different images on alternate fields. This allows to either display an image with higher vertical resolution (384 lines) or to display more than two colors in a single cell.
These effects won't display correctly unless you enable double scanline mode by enabling setting Double Line to Yes in the main menu. This can, however, cause display artifacts so it should not be enabled all the time.
Spec256 was a DOS-based emulator that allowed playing spectrum games that
have been enhanced to 256 colors. GZX can play enhanced Spec256 games
(albeit not perfectly). To load a Spec256 enhanced game, select Load Snapshot
from the main menu and load the .sna file from the Spec256 game folder
(it should also contain a .gfx file). You can also use Alt-N, Alt-M keys
to cycle between Spec256 backgrounds (as automatic switching is not
implemented).
$ git clone https://github.com/jxsvoboda/gzx gzx/trunk
$ cd gzx/trunk
You need a working GNU toolchain (GCC, Binutils, Make) (Linux or similar OS) and SDL 1.2 development package. To build Windows binaries, you need MingW64 cross-compiler.
To build just the 'gzx' binary
$ make
To build all binaries, including Windows binaries:
$ make all
You need a built HelenOS workspace and a working cross-compiler toolchain. If you don't have one, you need to do something like
$ git clone https://github.com/HelenOS/helenos.git helenos
$ cd helenos
$ sudo tools/toolchain.sh amd64
$ mkdir build
$ cd build
$ ../configure.sh amd64
$ ninja image_path
$ tools/export.sh export
You may need to have some development packages installed. For details, see http://www.helenos.org/wiki/UsersGuide/CompilingFromSource
Next you need to setup XCW tools which we use for the cross-compilation: $ PATH=$PATH:$PWD/tools/xcw/bin
Now go to your gzx workspace and off we go: $ cd ../gzx $ make test-hos
This will build the HelenOS binaries, install then to the HelenOS workspace and start emulation. Once in HelenOS start GZX by typing
# cd gzx
# ./gzx
If you want to only build the binaries without installing, type $ make hos
If you want to only build and install the binaries without starting emulation, type $ make install-hos
Now you need to go to root of your HelenOS workspace and type 'make' to re-build the OS image.
To check ccstyle type
$ make ccheck
This requires the ccheck tool from the Sycek project
Most of this emulator (i.e., source code, binaries, emulator font FONT.BIN, documentation) is free software, provided under an MIT-style license. The only exception are the enclosed ZX Spectrum ROM files. The copyright to the ROM files was held by Sinclair Research ltd. and later Amstrad plc. Amstrad allowed distributing ZX Spectrum ROM files toghether with emulator software.
Copyright (c) 1999-2025 Jiri Svoboda All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.