If you open up a Sinclair ZX Spectrum, you might expect to find a motherboard sprawling with chips—CPU, RAM, ROM, video logic, and sound circuits. Instead, you are greeted by a surprisingly empty board. The magic lies in one mysterious, black chip sitting smack in the center: the ULA (Uncommitted Logic Array).
Step 4 – Power
- Single 18650 or 1000mAh LiPo → 3.3V LDO (e.g., MCP1703).
- RP2040 and Z80 run at 3.3V. Use a level shifter if you use a 5V Z80 (but use a 3.3V version like Z84C0020PEC).
- Total current: ~100mA → >10 hours on 1000mAh.
To design a microcomputer using a ULA, you'll need to understand the basics of digital logic, computer architecture, and integrated circuit design. Here's a step-by-step guide to get you started: The ZX Spectrum ULA: How to Design a
Step 4: Video – From ULA to LCD
The original ULA spits out a 15.625kHz horizontal sync (PAL). A modern LCD expects 31kHz (VGA) or 74.25MHz (HDMI). Step 4 – Power
For the Spectrum, this meant Sinclair could take dozens of discrete logic chips—responsible for video timing, memory addressing, keyboard scanning, and sound generation—and compress them into a single, custom slab of silicon. Single 18650 or 1000mAh LiPo → 3
The ZX Spectrum ULA: Designing a Modern Retro Microcomputer The Sinclair ZX Spectrum remains a masterclass in minimalist engineering. At its heart lies the Uncommitted Logic Array (ULA), a custom chip that consolidated dozens of standard components into a single piece of silicon. Understanding the ULA is essential for any enthusiast looking to design a retro microcomputer or a portable modern recreation. The Heart of the Machine: The Ferranti ULA
