Original Ferranti ULA design documents for Sinclair's entire 1980s product line have surfaced on eBay and are now publicly available. The haul includes printouts, engineering drawings, and handwritten notes covering the ZX81, the ZX Spectrum, the ZX Printer, the Microdrive, the Spectrum Interface 1, and Sinclair's flat-screen TV. The Ferranti ULA, an Uncommitted Logic Array, was the single component that let Sinclair undercut every competitor while still shipping a functional ASIC at consumer price points.
IP ownership landed at Sky, the satellite broadcaster, through Amstrad's portfolio acquisition. Sky cleared the documents for public sharing with minimal restrictions. Everything is catalogued with download links in a Google Spreadsheet. The reversal engineering community has already worked over some of these chips, but several ULAs remain uncharted, and the documents expose version-to-version differences in the same ULA where engineers were quietly patching silicon bugs across production runs.
The full breakdown is in the Happy Little Diodes video linked in the original piece. Read it for the specific document categories, the version diff details, and context on which chips are still wide open for reverse engineering. This is primary source material that did not exist publicly 45 years after the silicon was fabbed.
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