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Clock Signal
What it is
Clock Signal is a free, open-source emulator for running classic software on Linux and macOS. It supports systems such as the BBC Micro, Apple II, Atari 2600, Commodore Vic-20, early Macintosh, MSX, Sega Master System, and ZX Spectrum. The project describes its Acorn Archimedes, Commodore Amiga, and early PC compatible emulation as less rounded than its other listed systems. When given disk, tape, or ROM media, CLK can identify and configure a machine, run required commands, and speed loading where feasible. It does not require an import process or take ownership of users’ files. The emulator processes video signals such as composite video and generates audio at the emulated machine’s source rate before filtering it for host output. Its README reports audio latency generally at 5–10 ms; display latency depends on host hardware. CLK attempts cycle-accurate emulation and says it succeeds in some cases. A BIOS is required. The project is MIT licensed, and Linux and macOS builds are available.
For and against
For
- Free and MIT licensed
- Supports a broad range of classic systems
- Analyzes media to configure a machine
- No file import procedure
Against
- BIOS support is required
- Some listed systems have less rounded emulation
- No Android support
The verdict
Clock Signal offers a free way to launch classic software on Linux and macOS, with media analysis to handle machine setup and loading. Its emulation is less rounded for some systems, and BIOS support is required.
Who it suits
Clock Signal suits Linux or macOS users who want to run classic software across a range of emulated machines. Users should be prepared to provide BIOS support.
Plans and prices
Clock Signal
Open-source emulator · macOS and Linux builds, plus source releases
Read 9 Oct 2026 · github.com
On the record
- Accuracy
- CLK attempts cycle-accurate emulation of all supported machines, and its README says this succeeds in some cases.github.com · read 9 Oct 2026
- Emulation status
- The README describes Acorn Archimedes, Commodore Amiga and early PC compatible emulation as less rounded than the other listed systems.github.com · read 9 Oct 2026
- File handling
- The README says CLK does not take ownership of users’ files and has no import procedure.github.com · read 9 Oct 2026
- Latency
- The README says audio latency is generally 5–10 ms and display latency is dictated by host hardware.github.com · read 9 Oct 2026
- License
- The GitHub repository identifies the project as MIT licensed.github.com · read 9 Oct 2026
- Linux and Unix builds
- A Qt-based Linux build is available as a Snap, and the README says Linux, BSD and other Unix-like systems can use OpenGL with Qt or SDL builds.github.com · read 9 Oct 2026
- macOS build
- The macOS application is native Cocoa and Metal, and macOS releases are hosted on GitHub.github.com · read 9 Oct 2026
- Purpose
- Clock Signal is an emulator designed to let users launch classic software directly without first learning how to use an emulator or the original machines.github.com · read 9 Oct 2026
- Recent release
- The GitHub releases page lists 2026-07-23 as the latest release and describes a fix for OpenGL output affecting several emulated systems on Qt and SDL targets.github.com · read 9 Oct 2026
- Signal processing
- CLK processes video signals such as composite video and generates audio at the emulated machine’s source rate before filtering it for host output.github.com · read 9 Oct 2026
- Single-step loading
- CLK analyzes disk, tape or ROM media to select and configure a machine, issue required commands and accelerate loading where feasible.github.com · read 9 Oct 2026
- Supported machines
- It emulates numerous classic systems, including the BBC Micro, Apple II, Atari 2600, Commodore Vic-20, early Macintosh, MSX, Sega Master System and ZX Spectrum.github.com · read 9 Oct 2026
