Gate array

A gate array is an approach to the design and manufacture of application-specific integrated circuits (ASICs) using a prefabricated chip with components that are later interconnected into logic devices (e.g. NAND gates, flip-flops, etc.) according to custom order by adding metal interconnect layers in the factory. It was popular during the upheaval in the semiconductor industry in the 1980s, and its usage declined by the end of the 1990s. Similar technologies have also been employed to design and manufacture analog, analog-digital, and structured arrays, but, in general, these are not called gate arrays. Gate arrays have also been known as uncommitted logic arrays (ULAs), which also offered linear circuit functions, and semi-custom chips. Gate arrays had several concurrent development paths. Ferranti in the UK pioneered commercializing bipolar ULA technology, offering circuits of "100 to 10,000 gates and above" by 1983. The company's early lead in semi-custom chips, with the initial application of a ULA integrated circuit involving a camera from Rollei in 1972, expanding to "practically all European camera manufacturers" as users of the technology, led to the company's dominance in this particular market throughout the 1970s. However, by 1982, as many as 30 companies had started to compete with Ferranti, reducing the company's market share to around 30 percent. Ferranti's "major competitors" were other British companies such as Marconi and Plessey, both of which had licensed technology from another British company, Micro Circuit Engineering. A contemporary initiative, UK5000, also sought to produce a CMOS gate array with "5,000 usable gates", with involvement from British Telecom and a number of other major British technology companies. IBM developed proprietary bipolar master slices that it used in mainframe manufacturing in the late 1970s and early 1980s, but never commercialized them externally. Fairchild Semiconductor also flirted briefly in the late 1960s with bipolar arrays diode–transistor logic and transistor-transistor logic called Micromosaic and Polycell.