The Zx Spectrum Ula- How To Design A Microcomputer -zx Design Retro Computer- (2027)

ZX Spectrum ULA: How to Design a Microcomputer , written by Chris Smith, is considered the definitive technical resource for understanding the custom "heart" of the Sinclair ZX Spectrum. The book documents Smith’s extensive reverse-engineering project, where he stripped the ULA chip down to its transistors to reveal its hidden logic and design secrets. Core Technical Focus

Understanding the ULA has led to a massive resurgence in "home-grown" Spectrums. Projects like the ZX Spectrum ULA: How to Design a Microcomputer

References

1. Smith, C. (2014). The ZX Spectrum ULA: How to Design a Microcomputer. Createspace Independent Publishing.
2. Altwasser, R. (1982). "Internal Ferranti Design Notes for ULA 5C112E." (Unpublished, reconstructed via die photography).
3. Vickers, S. (1982). ZX Spectrum Basic Programming. Sinclair Research Ltd.
4. Retro Techie. (2019). "Harlequin 128K: An Open Source ZX Spectrum Clone." GitHub Repository.
5. O’Regan, G. (2016). The Ferranti ULA: The British Silicon Story. Computing History Journal, 12(3), 45-52.

The "Strict" Timing: The ULA demands that DRAM refresh and CPU access occur in specific 4MHz clock phases. The Z80 CPU (running at 3.5MHz) must be halted (via the /WAIT pin) during the ULA’s screen drawing phases. This is the famous contention. Smith, C