: To avoid collisions, the ULA has priority access to the "lower RAM" (0x4000 to 0x7FFF) for video drawing. If the CPU tries to access this area at the same time, the ULA halts the CPU clock, a behavior known as contention .
In the early 1980s, Richard Altwasser and the Sinclair team faced a challenge: build a color computer for under £100. Their solution was the Ferranti ULA, a "gate array" precursor to modern FPGAs. The ULA performed four critical roles: : To avoid collisions, the ULA has priority
In 1982, most computers used dozens of individual chips. Sinclair contracted Ferranti to build a Uncommitted Logic Array (ULA) . This was a primitive form of a modern FPGA. Integration: It combined roughly 40 discrete chips into one. Cost Reduction: Fewer parts meant a lower retail price (£125). Video Master: Their solution was the Ferranti ULA, a "gate
Recreating the ZX Spectrum experience hinges on reproducing both function and timing. Using an FPGA to implement a modern ULA lets you preserve the machine’s behavioral quirks (what made the Spectrum special) while adding modern conveniences for portability. Start with a focused FPGA video/DRAM prototype, iterate with a simple ROM and Z80 core, and build outward—balancing authenticity and usability to produce a compact, lovable retro microcomputer. This was a primitive form of a modern FPGA