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I’ve often wondered what the differences between the ULA models for the ZX Spectrum are.
Fortunately Chris Smith did a brilliant job of writing a comprehensive technical masterpiece about the ZX Spectrum’s ULA and its history.
Underneath a short summery of the different ULA models and in which ZX Spectrum issues they were used:
- 5C102E: ZX Spectrum Issue 1 boards
- 5C112E: ZX Spectrum Issue 2 boards
- 6C001E-5: the first 6000 series ULA, probably for ZX Spectrum Issue 3 boards (not documented in Chris Smith’s book)
- 6C001E-6: ZX Spectrum Issue 3 boards
- 6C001E-7: ZX Spectrum Issue 4A boards (and higher board issues)
For the exact differences I recommend to buy “The ZX Spectrum ULA – How To Design A Microcomputer” (ISBN 978-0-9565071-0-5) by Chris Smith yourself.
But for ZX Spectrum enthousiast like myself who need to know about compatibility:
- The 6C001E-7 ULA version can be used on all ZX Spectrum 48K board issues.
- The ZX Spectrum Issue 4A and above will ONLY work reliable with the 6C001E-7 ULA version; don’t use another ULA in an Issue 4A board or later Issue.
Of course it’s best to use the exact ULA model that corresponds to the ZX Spectrum Issue as listed above; ULA’s are getting more rare each day.