Spec

A ZX Spectrum 48K emulator written in Unleashed Pascal, rendered with raylib. Tested on Windows, Linux, macOS and the Raspberry Pi — including bare DRM/KMS on the Pi with no desktop, so it turns straight into a full-screen Spectrum.

Features

• Accurate Z80 core — built on the Z80 CPU library by Manuel Sainz de Baranda y Goñi, via Pascal bindings by Zoran Vučenović.
• Faithful ULA emulation — memory-contention timing, mid-frame border-color effects.
  • Direct-pixel video — the Spectrum bitmap is written straight into the frame buffer through an attribute lookup table, then scales up to any window size.
• CRT / display modes (F11 to cycle):
  • Color CRT — curvature, scanlines, phosphor glow
  • Black & white CRT
  • Modern (smooth) and Modern (sharp)
  • Modern (scaleFX) — pixel-art upscaling
• Sound — beeper output and audible tape loading, with turbo/fast-forward.
• Media:
  • .z80 snapshots — load and save
  • .tap tapes — fast-load trap, auto-started on LOAD ""
  • .wav tapes — real-time EAR-line playback for turbo-loaders and custom loading schemes, with auto-pause on silence
• On-screen menu (OSD) with a browsable game catalog — a scrolling list of titles with a live screenshot preview beside each.
• On-screen keyboard overlay for the Spectrum's keyword layout.
• Configurable input — remap the keyboard, bind a gamepad, and switch joystick emulation between Kempston, Cursor/Protek, Sinclair and Spanish (QAOPM).
• Per-game quick-save / quick-load.
• Screenshot capture to PNG.

Not implemented

This is a focused 48K emulator. It deliberately leaves out:

• A hand-written Z80 core — instruction decoding is delegated to the external Z80 C library rather than implemented in Pascal.
• 128K models — no 128K/+2/+3 memory paging, so 128K-only releases won't run.
• AY-3-8912 sound — beeper only; no AY music.
• Disk interfaces — no +3 disk, Beta/TR-DOS, .dsk/.trd/.scl, or Interface 1 / microdrive.
• Other snapshot/tape formats — no .sna, .szx, .tzx, or .rzx; loading is limited to .z80, .tap and .wav.

First run: unsigned builds

The released binaries are not code-signed or notarized, so Windows and macOS will refuse to launch them until you say otherwise. Nothing is wrong with the download — the operating system simply has no certificate to check it against. If you would rather not bypass the warning, build from source instead; a binary you compile yourself is not quarantined.

macOS

Gatekeeper reports "Apple could not verify 'spec' is free of malware" and offers only Move to Bin. Solution:

• Strip the quarantine flag:

  xattr -dr com.apple.quarantine spec.app

Windows

SmartScreen shows "Windows protected your PC". Click More info → Run anyway. If the executable came out of a ZIP, Windows may also mark it as blocked; clear that with either:

• File Properties — right-click spec.exe → Properties → tick Unblock at the bottom of the General tab → OK.

• PowerShell:

  Unblock-File .\spec.exe

Some antivirus products flag unsigned Pascal/raylib executables as unknown rather than malicious; you may need to add an exclusion for the folder.

Controls

Function keys

Key	Action
F1	Open the emulator menu (also the gamepad's Menu button)
F2	Quick-save the current machine state
F3	Quick-load the last quick-saved state
F5	Play/pause the loaded .wav tape (only while a tape is loaded)
F6	Cycle to the next joystick emulation mode
F7	Decrease volume — hold Shift for overscan instead
F8	Increase volume — hold Shift for overscan instead
F9	Toggle the on-screen keyboard overlay
F10	Toggle fullscreen
F11	Switch TV-set / display mode

Other keys

Key	Action
Tab	Jump straight to the catalog (skips the menu's top page)
Esc	Press once to arm quit, press again within 2 s to quit
` (grave)	Hold for turbo (fast-forward)
Scroll Lock	Save a screenshot PNG of the current display

Saved files land in the folder described under Where files are written.

Getting the games

No games or tape images ship with the emulator. Drop .z80, .tap or .wav files anywhere and open them from the menu (Load file).

To use the built-in catalog, create a catalog/ folder next to the binary containing a catalog.csv:

name,file
Arkanoid,arkanoid.z80
Batty,batty.tap

Put each file in the same folder. An optional screenshot with the same base name (arkanoid.png) is shown in the preview pane.

Where the catalog is looked for

[Files] CatalogPath in spec.conf names the folder outright:

[Files]
CatalogPath=~/Games/Spectrum/catalog

A leading ~ is expanded; the path is otherwise taken at its word, and nothing else is tried — so a typo shows up as an empty catalog rather than a different one quietly loading in its place.

Left unset, the folder is looked for in the working directory first, then next to the binary. On macOS a bundle adds two more places, since the binary itself is buried in spec.app/Contents/MacOS/:

Where	For
Next to spec.app	A catalog the player can add games to
spec.app/Contents/Resources/catalog/	A catalog shipped inside the app

Outside beats inside, so a catalog next to the bundle overrides one shipped within it. A catalog in Contents/Resources/ is covered by the code signature — which is what stops the player adding to it, and means it has to be in place before macos-bundle.sh signs. Running with LogLevel=0 prints which one was picked.

Where files are written

Snapshots, taped programs, screenshots and spec.conf all go to the same folder:

Platform	Folder
Windows, Linux	The folder the emulator was started from
macOS	~/Library/Application Support/spec/

macOS is the odd one out because Finder launches an .app with the root of the disk as its working directory, and writing next to the bundle would break the signature it was sealed with. Setting SPEC_DATA_DIR overrides the choice everywhere, and [Files] SavePath moves the snapshots (and with them the screenshots and taped programs) somewhere else again.

Configuration

Settings live in spec.conf (INI format) — see the table above for where — and are written back when you change them in the menu. Notable sections:

[Window]
Width=720
Height=576
Fullscreen=1

[Display]
TVMode=0          ; 0=Colour CRT, 1=BW CRT, 2=Modern smooth, 3=Modern sharp, 4=scaleFX
Overscan=16
Curvature=8

[Audio]
Volume=0.65
Muted=0

[Files]
SavePath=         ; empty = the default write folder; ~ is expanded
CatalogPath=      ; empty = search the usual places

[Joystick]
Index=1           ; 0=none, then Kempston, Cursor, Sinclair, Spanish

[Bindings]
Fire 1=key:Left ALT
Fire 2=key:Right ALT

[Bindings:usb gamepad]
Left=pad:DPAD_LEFT, axis:LEFT_X-
Fire 1=pad:FACE_DOWN

Building

Requirements

• Unleashed Pascal compiler
• ray4laz package installed (provides the raylib bindings and libraries).

Desktop (Windows / Linux / macOS)

Open spec.lpi in Lazarus (Unleashed IDE) and build the Release mode, or from the command line:

lazbuild --build-mode=Release spec.lpi

The native Z80 shared library for your platform is in lib/ (libZ80.so, Z80.dll, libZ80.dylib). It is not linked in — the emulator opens it at runtime — and it is looked for, in order, at $LIBZ80_PATH, then ./ and ./lib/ relative to the working directory, then the same two next to the executable, and on macOS in the bundle's Contents/Frameworks/. Keeping it beside the executable covers every case.

Project layout

Path	Purpose
spec.lpr / main.pas	Application entry point and main loop
spectrum.pas	ZX Spectrum 48K machine — ULA, video, tape, contention
Z80/Z80.pas	Pascal bindings for the Z80 CPU library
keyboards.pas / joysticks.pas / inputs.pas	Input handling and mapping
osdmenu.pas / catalogs.pas	On-screen menu and game catalog
appsettings.pas	spec.conf reader/writer
utils.pas	Platform odds and ends, including where the emulator writes
shaders/	GLSL fragment shaders for the display modes
rom/48.rom	Spectrum 48K ROM
macos-bundle.sh	Assembles and signs spec.app

Licensing

The emulator's own source code is released under the MIT License (see LICENSE).

Bundled third-party components keep their own terms:

• ZX Spectrum 48K ROM (rom/48.rom) — © Amstrad plc. Amstrad have given permission to redistribute their copyrighted material for use in emulators, provided the copyright messages are not altered; Amstrad retain that copyright. See licenses/Amstrad ROM.txt.
• Z80 CPU library — © Manuel Sainz de Baranda y Goñi, GNU LGPL v3. See licenses/Z80.txt.
• Fake Receipt font (fonts/) — Raymond Larabie, released CC0. See licenses/Fake Receipt.txt.

Game snapshots and tape images are the copyright of their respective authors and are not distributed with this project.