This article is not just a history lesson. It is a design autopsy. By understanding how Sir Clive Sinclair’s team—specifically engineer Richard Altwasser—used the ULA, you will learn the fundamental principles of how to design a microcomputer when every gate and every penny counts. Before we open the schematic, you must adopt the 1982 mindset. You are not Apple. You cannot use a dozen LS TTL chips. You have to sell this computer for under £100.
"If a function can be done in software, do it in software. If it saves a chip to do it in hardware, do it in the ULA." This article is not just a history lesson
Unlike linear framebuffers (like the VIC-II in the C64), the Spectrum’s screen is a fractal nightmare. The memory map looks like this: Before we open the schematic, you must adopt
The ZX80 and ZX81 used discrete logic to generate video. The Spectrum needed color, but adding more chips would kill the budget. The solution was the —specifically the Ferranti ULA. You have to sell this computer for under £100