💡 If you're building a portable, focus on the keyboard . The Spectrum's "one-key-word" entry system makes it uniquely suited for small devices where a full QWERTY layout might be cramped.
Let’s design a modern, portable Spectrum clone. We will call it the "ZX LapPak." 💡 If you're building a portable, focus on the keyboard
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 SRAM chip. We will call it the "ZX LapPak
It handles the "beeper" sound, the tape recorder interface for saving/loading data, and the iconic rubber keyboard matrix. Designing a Modern "Retro" Version It handles the "beeper" sound, the tape recorder
This article dissects the ULA’s architecture and then applies those lessons to the practical challenge of building a handheld, battery-powered Spectrum-compatible machine.
In the early 80s, building a microcomputer usually required a "glue logic" board filled with standard chips to manage memory and video. Sinclair contracted to create a custom ULA—a semi-custom chip where the logic gates were pre-fabricated, but the final metal layer was "committed" to Sinclair’s specific design. This reduced the part count, lowered costs, and made the Spectrum’s small form factor possible. Key Functions
Use a Xilinx or Altera chip to recreate the ULA logic (see the project for schematics). Discrete Logic: Use 74-series chips (this results in a very large board). Microcontroller:
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