When designing a modern, portable ZX-compatible computer, engineers typically choose between a system based on original/reproduction silicon or a hardware description language (HDL) implementation. For portability and reliability, an FPGA or a fast CPLD implementation is highly recommended.
The classic Spectrum keyboard is a membrane matrix that feels uniquely rubbery. For a modern portable computer:
When routing your custom PCB for a portable Spectrum clone, keep this architecture checklist handy:
Replacing a faulty original ULA or building a system from scratch is best achieved via programmable logic. Chris Smith's landmark book, The ZX Spectrum ULA: How to Design a Microcomputer , reverse-engineered the exact schematic of the chip. You can implement this logic using: Xilinx XC95144XL CPLD Go to product viewer dialog for this item. For a modern portable computer: When routing your
Because an entire 8×8 block shares just one Ink color and one Paper color, moving sprites cause colors to spill into adjacent blocks. This is . Embracing or perfectly simulating this limitation is vital for an authentic retro microcomputer design. Designing a Modern Portable ZX Spectrum
By building your own portable microcomputer around these classic principles, you gain a deep appreciation for low-level system architecture while creating a piece of functional, pocket-sized nostalgia.
This public link is valid for 7 days and shares a thread, including any personal information you added. This link or copies made by others cannot be deleted. If you share with third parties, their policies apply. Can’t copy the link right now. Try again later. Because an entire 8×8 block shares just one
To design a microcomputer using the principles of the ZX Spectrum ULA, you are looking at designing a 4-bit, 8-bit, or small 16-bit system where are paramount. Core Components of a ULA-Based System: CPU: Typically a Zilog Z80A running at 3.5MHz. RAM/ROM: 16K or 48K of DRAM/SRAM and ROM. The ULA (or FPGA equivalent): The master coordinator. Design Principles for Retro Computers:
Because the ULA controls the timing, it can siphon data from the RAM during the blanking intervals (the moments the TV electron gun moves back to the top of the screen). This creates the famous "contended memory" timing—a headache for emulator authors but a genius cost-saving hack that required fewer chips.
The ULA was a tightly coupled video+memory controller . You cannot make a simple ZX clone without replicating this arbitration. If you share with third parties
The ULA is the Spectrum's heart, but its most brilliant trick is handling video. Most computers of the era used dedicated video display controllers (like the C64’s VIC-II). The Spectrum’s ULA generates the video signal directly.
It has: