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Early gate arrays were low performance and relatively large and expensive compared to state-of-the-art n-MOS technology then being used for custom chips. CMOS technology was being driven by very low power applications such as watch chips and battery operated portable instrumentation, not performance. They were also well under the performance of the existing dominant logic technology, transistor–transistor logic families. However, there were many niche applications where they were invaluable, particularly in low power, size reduction, portable and aerospace applications as well as time-to-market sensitive products. Even these small arrays could replace a board full of transistor–transistor logic gates if performance were not an issue. A common application was combining a number of smaller circuits that were supporting a larger LSI circuit on a board was affectionately known as "garbage collection". And the low cost of development and custom tooling made the technology available to the most modest budgets. Early gate arrays played a large part in the [[Citizens band radio#1970s popularity|CB craze in the 1970s]] as well as a vehicle for the introduction of other later mass-produced products such as modems and cell phones.
By the early 1980s gate arrays were starting to move out of their niche applications to the general market. Several factors in technology and markets were converging. Size and performance were increasing; automation was maturing; technology became "hot" when in 1981 IBM introduced its new flagship [[IBM 308X|3081]] mainframe with CPU comprising gate arrays,; they were used in a consumer product, the ZX81; and new entrants to the market increased visibility and credibility.<ref>{{cite book |first=Chris |last=Smith |title=The ZX Spectrum ULA: How To Design A Microcomputer |publisher=ZX Design and Media |oclc=751703922 |date=2010 |isbn=9780956507105 |pages= |url=http://www.zxdesign.info/book/insideULA.shtml}}</ref>
In 1981, [[Wilfred Corrigan]], Bill O'Meara Rob Walker and Mitchell "Mick" Bohn founded [[LSI Corporation|LSI Logic]].<ref>{{Cite web|url=http://www.computerhistory.org/collections/catalog/102746194|title=LSI Logic oral history panel {{!}} 102746194|website=Computer History Museum|access-date=2018-01-28}}</ref> Their initial intention was to commercialize emitter coupled logic gate arrays, but discovered the market was quickly moving towards CMOS. Instead they licensed CDI's silicon gate CMOS line as a second source. This product established them in the market while they developed their own proprietary 5 micron 2-layer metal line. This latter product line was the first commercial gate array product amenable to full automation. LSI developed a suite of proprietary development tools that allowed users to design their own chip from their own facility by remote login to LSI Logic's system.
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=== Decline ===
While the market boomed, profits for the industry were lacking. Semiconductors underwent a series of rolling [[List of recessions in the United States|recessions]] during the 1980s that created a boom-bust cycle. The 1980 and
As of the early 21st century, the gate array market was a remnant of its former self, driven by the FPGA conversions done for cost or performance reasons. IMI moved out of gate arrays into mixed signal circuits and was later acquired by Cypress Semiconductor in 2001; CDI closed its doors in 1989; and LSI Logic abandoned the market in favor of standard products and was eventually acquired by Broadcom.<ref>{{Cite web|url=http://www.computerhistory.org/siliconengine/companies/|title=Companies|website=The Silicon Engine|publisher=Computer History Museum|access-date=2018-01-28}}</ref>
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The earliest gate arrays comprised [[bipolar transistors]], usually configured as high performance [[transistor–transistor logic]], [[emitter-coupled logic]] or [[current-mode logic]] logic configurations. [[CMOS]] (complementary [[metal-oxide-semiconductor]]) gate arrays were later developed and came to dominate the industry.
Gate array master slices with unfinished chips arrayed across a [[wafer (electronics)|wafer]] are usually prefabricated and stockpiled in large quantities regardless of customer orders. The design and fabrication according to the individual customer specifications can be finished in a shorter time than [[standard cell]] or [[full custom]] design. The gate array approach reduces the non recurring engineering [[Photomask|mask]] costs as fewer custom masks need to be produced. In addition, manufacturing test tooling lead time and costs are reduced
An application circuit must be built on a gate array that has enough gates, wiring and I/O pins. Since requirements vary, gate arrays usually come in families, with larger members having more of all resources, but correspondingly more expensive. While the designer can fairly easily count how many gates and I/Os pins are needed, the number of routing tracks needed may vary considerably even among designs with the same amount of logic. (For example, a [[crossbar switch]] requires much more routing than a [[systolic array]] with the same gate count.) Since unused routing tracks increase the cost (and decrease the performance) of the part without providing any benefit, gate array manufacturers try to provide just enough tracks so that most designs that will fit in terms of gates and I/O pins can be routed. This is determined by estimates such as those derived from [[Rent's rule]] or by experiments with existing designs.
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Gate arrays were used widely in the [[home computer]] market in the United Kingdom in the early 1980s, including in the [[Sinclair ZX81]] and [[Sinclair Spectrum]], the [[BBC Micro]] and [[Acorn Electron]], and the [[Commodore Amiga]].
== References ==
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