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

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