The ZX Spectrum Reverse Engineering and Clone Desgin Blog


A site dedicated to the reverse engineering of the ZX Spectrum and related projects.

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The Beginning

Feb 02, 2007

Please browse the index page for a full list of sections in this blog.

It was time to sort out the atic. Whilst going through box after box of archived rubbish, I can across some old Spectrum and random electronic designs that I'd put to paper back in the late 80's early 90's.

Among these papers I found an Eprom programmer (and later a 99% complete implementation on Vero board) and the beginnings of a video display design...

The timing calculations scribbled on the design looked fairly 'official' (presumable I'd got them from some timing reference) and it was interesting to see that I had been attempting both Spectrum-style colour as well as a 4bpp mode.

And that got me wondering... Exactly how difficult is it to implement a working clone of the ZX Spectrum using nothing more than discrete logic?

A quick bit of surfing came up with two projects of interest, SpeccyBob and Chrome. SpeccyBob is implemented in discrete logic, whereas Chrome is mostly implemented through a PLA/PLG. I noted however that neither of the projects showed the effort or the pitfalls in coming up with a working ZX Spectrum Clone design. This I felt would have been useful for anyone interested in the design process and the clever little solutions found for the quirks and characteristics of that wonderful Sinclair machine.

So this site is dedicated to the design of a ZX Spectrum Clone. In true research lab fashion this site will document the complete progress: the questions, the answers, the mistakes and the eureka moments. At the end of it we may even get a working ZX Spectrum clone...

My intention is not to use SpeccyBob or Chrome as references as I'm interested in working through and documenting the whole design process of a Sinclair clone.