Full custom

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Full custom design is a methodology for designing integrated circuits by specifying the layout of each individual transistor and the interconnections between them. The alternative to full custom design is the use of standard cell libraries.(Note standard cell libraries are themselves designed using full custom design techniques.) Full custom design maximizes the performance of the chip, and minimizes its area, but is extremely labor-intensive to implement. Full custom design is limited to ICs that are to be fabricated in extremely high volumes, notably certain microprocessors and a small number of ASICs. The main factor effecting the design and production of ASICs is the high cost of mask sets and the requisite EDA design tools. The mask sets are required in order to transfer the ASIC designs onto the wafer.