Gate array

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. 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 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; the technology became "hot" when in 1981 IBM introduced its new flagship 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.

In 1981, Wilfred Corrigan, Bill O'Meara, Rob Walker, and Mitchell "Mick" Bohn founded LSI Logic. 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.

Sinclair Research ported an enhanced ZX80 design to a ULA chip for the ZX81, and later used a ULA in the ZX Spectrum. A compatible chip was made in Russia as T34VG1. Acorn Computers used several ULA chips in the BBC Micro, and later a single ULA for the Acorn Electron. Many other manufacturers from the time of the home computer boom period used ULAs in their machines. The IBM PC took over much of the personal computer market, and the sales volumes made full-custom chips more economical. Commodore's Amiga series used gate arrays for the Gary and Gayle custom chips, as their code names may suggest.

In an attempt to reduce the costs and increase the accessibility of gate array design and production, Ferranti introduced in 1982 a computer-aided design tool for their uncommitted logic array (ULA) product called ULA Designer. Although costing £46,500 to acquire, this tool promised to deliver reduced costs of around £5,000 per design plus manufacturing costs of £1-2 per chip in high volumes, in contrast to the £15,000 design costs incurred by engaging Ferranti's services for the design process. Based on a PDP-11/23 minicomputer running RSX/11M, together with graphical display, keyboard, "digitalizing board", control desk and optional plotter, the solution aimed to satisfy the design needs of gate arrays from 100 to 10,000 gates, with the design being undertaken entirely by the organisation acquiring the solution, starting with a "logic plan", proceeding through the layout of the logic in the gate array itself, and concluding with the definition of a test specification for verification of the logic and for establishing an automated testing regime. Verification of completed designs was performed by "external specialists" after the transfer of the design to a "CAD center" in Manchester, England or Sunnyvale, California, potentially over the telephone network. Prototyping completed designs took an estimated 3 to 4 weeks. The minicomputer itself was also adaptable to run as a laboratory or office system where appropriate.

Ferranti followed up on the ULA Designer with the Silicon Design System product based on the VAX-11/730 with 1 MB of RAM, 120 MB Winchester disk, and utilising a high-resolution display driven by a graphics unit with 500 KB of its own memory for "high speed windowing, painting, and editing capabilities". The software itself was available separately for organisations already likely to be using VAX-11/780 systems to provide a multi-user environment, but the "standalone system" package of hardware and software was intended to provide a more affordable solution with a "faster response" during the design process. The suite of tools involved in the use of the product included logic entry and test schedule definition (using Ferranti's own description languages), logic simulation, layout definition and checking, and mask generation for prototype gate arrays. The system also sought to support completely auto-routed designs, utilising architectural features of Ferranti's auto-routable (AR) arrays to deliver a "100-percent success auto-layout system" with this convenience incurring an increase in silicon area of approximately 25 percent.

Other British companies developed products for gate array design and fabrication. Qudos Limited, a spin-off from Cambridge University, offered a chip design product called Quickchip available for VAX and MicroVAX II systems and as a complete $11,000 turnkey solution, providing a suite of tools broadly similar to those of Ferranti's products including automatic layout, routing, rule checking and simulation functionality for the design of gate arrays. Qudos employed electron beam lithography, etching designs onto Ferranti ULA devices that formed the physical basis of these custom chips. Typical prototype production costs were stated as £100 per chip. Quickchip was subsequently ported to the Acorn Cambridge Workstation, with a low-end version for the BBC Micro, and to the Acorn Archimedes.

Indirect competition arose with the development of the field-programmable gate array (FPGA). Xilinx was founded in 1984, and its first products were much like early gate arrays, slow and expensive, fit only for some niche markets. However, Moore's law quickly made them a force and, by the early 1990s, were seriously disrupting the gate array market.

Designers still wished for a way to create their own complex chips without the expense of full-custom design, and eventually, this wish was granted with the arrival of not only the FPGA, but complex programmable logic device (CPLD), metal configurable standard cells (MCSC), and structured ASICs. Whereas a gate array required a back-end semiconductor wafer foundry to deposit and etch the interconnections, the FPGA and CPLD had user-programmable interconnections. Today's approach is to make the prototypes by FPGAs, as the risk is low and the functionality can be verified quickly. For smaller devices, production costs are sufficiently low. But for large FPGAs, production is very expensive, power-hungry, and in many cases, do not reach the required speed. To address these issues, several ASIC companies like BaySand, Faraday, Gigoptics, and others offer FPGA to ASIC conversion services.

While the market boomed, profits for the industry were lacking. Semiconductors underwent a series of rolling recessions during the 1980s that created a boom-bust cycle. The 1980 and 1981–1982 general recessions were followed by high-interest rates that curbed capital spending. This reduction played havoc on the semiconductor business, which at the time was highly dependent on capital spending. Manufacturers desperate to keep their fab plants full and afford constant modernization in a fast-moving industry became hyper-competitive. The many new entrants to the market drove gate array prices down to the marginal costs of the silicon manufacturers. Fabless companies such as LSI Logic and CDI survived on selling design services and computer time rather than on production revenues.

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.

Gate arrays were used widely in the home computers in the early to mid 1980s, including in the ZX81, ZX Spectrum, BBC Micro, Acorn Electron, Advance 86, and Commodore Amiga.

In the 1980s, the Forth Novix N4016 and HP 3000 Series 37 CPUs, both stack machines were implemented by gate arrays as were some graphic terminal functions. Some supporting hardware in at least 1990s DEC and HP servers was implemented by gate arrays.