Hackaday reports that Happy Little Diodes acquired a collection of original Ferranti design documents on eBay. The archive contains printed files, engineering drawings and handwritten notes about Sinclair’s Uncommitted Logic Arrays, or ULAs. These chips helped Sinclair deliver sophisticated hardware at low prices during the 8-bit home-computer boom of the early 1980s.

The documents cover the ZX81, ZX Spectrum, ZX printer, ZX Microdrive, Spectrum Interface 1 and a small flat-screen TV. Some Sinclair ULAs have already been reverse engineered, but the newly surfaced material includes parts that have not yet been studied in that way. It also records differences between ULA revisions made to correct hardware bugs.

The intellectual property is now held by Sky through its ownership of Amstrad’s portfolio. Sky allowed the historical documents to be published with minimal alterations. A Google spreadsheet catalogs the files and provides download links.