The Zx Spectrum Ula- How To Design A Microcomputer -zx Design Retro Computer- [cracked] -

Chris Smith

ZX Spectrum ULA: How to Design a Microcomputer , written by , 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

• Derive pixel/character rates, generate necessary phase relationships with master clock.

Richard Altwasser

The task fell to engineer . While Clive Sinclair obsessed over the sleek case design and the price point, Altwasser had to figure out how to cram the complexity of a color computer into a single piece of silicon. He chose an Uncommitted Logic Array from Ferranti—a type of semi-custom chip that was essentially a "blank slate" of logic gates waiting to be wired together. The Design: Engineering on the Edge Chris Smith ZX Spectrum ULA: How to Design

• The ULA has a row counter (0 to 191).
• It needs to find the pixel bytes quickly. It splits the row number into three parts: which third of the screen (0,1,2), which character row (0-7), and which pixel line within that character row.
• It shifts and masks these bits to form a linear address. This required 3 adders inside the ULA—a huge cost in 1982, but cheaper than a multiplier.

Ferranti ULA

At the center of the ZX Spectrum's design was the , a semi-custom logic chip that allowed Clive Sinclair to significantly reduce manufacturing costs. The ULA was responsible for several critical functions: Richard Altwasser The task fell to engineer

, based on the definitive research by Chris Smith in his landmark book, The ZX Spectrum ULA: How to Design a Microcomputer What is a ULA? which character row (0-7)