The Zx Spectrum Ula How To Design A Microcomputer Zx Design Retro Computer Portable -

The ZX Spectrum is a landmark in home computing, not because of its off-the-shelf components, but because of one chip: the Uncommitted Logic Array (ULA). Designed by Richard Altwasser and fabricated by Ferranti, this 40-pin chip replaced dozens of TTL logic chips, slashing costs and enabling Sinclair to deliver a color computer for under £125 in 1982.

To build a modern portable "ZX-like" computer, you don't need to source a vintage ULA. Instead, you must understand its functions and replicate or re-imagine them using modern hardware. The ZX Spectrum is a landmark in home

  • Preserve attribute-based color system and flash/bright behaviors, border handling, and contention timing for accurate effects.
  • Offer scanline and scaling modes in a menu (but keep original timing available).

    • The original Spectrum’s 16K or 48K of DRAM is a nightmare for portables. DRAM requires -5V, +12V, and +5V, plus constant refresh. Instead, use a single 512Kx8 AS6C4008 SRAM chip. The original Spectrum’s 16K or 48K of DRAM

    To design a new retro computer, you must first understand the original’s core. In most 8-bit computers (like the Commodore 64 or Apple II), discrete chips handle video, I/O, memory arbitration, and clock generation. Sinclair did something radical: they shoved almost all of that into a single ULA (a Ferranti-produced chip). plus constant refresh. Instead

  • Option B — Discrete logic + CPLD for partial ULA functions.
  • Option C — Software emulation on microcontroller/SoC (RPi/ARM).