Gate array-History-Custom Design Circuit
Board Electronic Pcb
Sinclair ZX81 ULA
A gate array or uncommitted logic array (ULA) is an approach to the design and manufacture of application-specific integrated circuits (ASICs), using a prefabricated chip with active devices like NAND-gates, that are later interconnected according to a custom order by adding metal layers in the factory.
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. Ferranti in the UK pioneered ULA technology, then later abandoned this lead in semi-custom chips. 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.
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 the field-programmable gate array (FPGA), complex programmable logic device (CPLD), Metal Configurable Standard Cells (MCSC), and structured ASIC. Whereas a ULA required a semiconductor wafer foundry to deposit and etch the interconnections, the FPGA and CPLD had programmable interconnections. Today's approach is to make the prototypes by FPGAs, as the risk is low and the functionality can be verified quickly, but for production FPGAs are very expensive, power hungry, and in many cases do not reach the required speed. Here come the "FPGA to ASIC" conversion which is supported by several ASIC companies like BaySand, Faraday, Gigoptics and others.