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Clock Signal vs USP - ZX Spectrum Emulator: catalog facts
Clock Signal	USP - ZX Spectrum Emulator
Free Free and open source, developed by Tom Harte.	Free Free and open source under the GPL-3.0-or-later licence.
macOS, Linux	Android
Emulates a wide range of 8- and 16-bit computers and consoles in one program Designed around low input and display latency	Wide file format support including tzx, trd and rzx Emulates Pentagon 128K with AY/YM sound and Beta Disk
No separate project homepage beyond the GitHub repository Some systems need original ROM images supplied by the user	Emulates the ZX Spectrum family only Sparse project homepage and documentation
Downloadable app	Downloadable app
Open source	Open source
License: MIT	License: GPL-3.0-or-later
No account needed	Not stated if an account is needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.