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

Since original Ferranti chips are rare, you have three modern paths: CPLD/FPGA:

Smith explains the origin of famous hardware "bugs," such as the "Snow Effect" (caused by memory contention) and the non-standard composite sync pulses that many modern TVs struggle to process.

Forget the original ULA. You need an (Field Programmable Gate Array). The cheapest and most documented for this task is the ICE40UP5K or the Xilinx XC9572XL for a CPLD, but for a full ULA+Z80, use an EP4CE10 (Cyclone IV) or an Lattice iCE40 HX8K .

For beginners, an RP2040-based emulated version is faster to prototype. But for the true “design a microcomputer” experience—understanding contention, video timing, and memory arbitration—an FPGA ULA is the definitive modern method.

(CMOS version). It still runs at 3.5MHz and is widely available.

The ULA is both the genius and the obstacle in designing a portable ZX Spectrum. For a practical, battery-powered retro computer that feels authentic, an FPGA-based ULA replacement offers the perfect balance of accuracy, low power, and compact size. By combining an FPGA with a discrete CMOS Z80, 64KB SRAM, and a small LCD, you can build a handheld Spectrum that runs original software, behaves exactly like the 1982 machine, and fits in a coat pocket.

If your goal is a portable device, focus on these integration steps: Building a Pocket ZX Spectrum | PDF - Scribd