Clock Signal

About

Clock Signal (CLK) is a Mac emulator designed to stay out of the way. Users double-click classic software in Finder, on the desktop, or in the Dock, and it runs. The app automatically selects and configures the appropriate machine for any supplied disk, tape, or ROM, issues the necessary loading commands, and provides accelerated loading where feasible. No manual machine setup, media insertion, or import step is required, and CLK does not take ownership of your files.

The emulator aims for accurate output by processing signals the way the original hardware does. For example, the emulated Vic-20's composite video is decoded by the host GPU, so composite artefacts appear as they would on the real machine, and audio is generated at the machine's native rate before being filtered down. The emulated display is a CRT with phosphor decay, and it can produce frames at the host monitor's full refresh rate. Latency is set by the host hardware, with audio latency generally around 5–10ms.

CLK covers a wide range of platforms, including the Acorn Electron, Amstrad CPC, Apple II/IIe, Atari 2600 and ST, BBC Micro, Commodore Vic-20 and Plus 4, Macintosh 128K through Plus, MSX, Sega Master System, Sinclair ZX80/81 and ZX Spectrum, Tandy CoCo, and Thomson MO5/6, among others. On the Mac it is a native Cocoa and Metal application. Source code is MIT-licensed and hosted on GitHub, which also provides macOS builds and a Qt-based Linux build distributed as a Snap.