ASIC stands for the abbreviation of Application Specific Integrated Circuits. It means an integrated circuit designed for a specific application. An application could be a microprocessor, cell phone, modem, router, etc., The respective ASIC will have its own architecture, need to support its own protocol requirements . In todays ASIC has a complete system in a single often called as System on a Chip(SOC).
The flow involved to achieve this could be semi custom or full custom. The various cost function for an ASIC chip could be "Area, Timing, Power" Targets.
Basically microprocessor involves full custom. Full custom designs take lot of time to design. Full custom designs are used to achieve high frequency targets.
Where as in a semi custom flow, initially the standard cells are pre designed based on the characterization of the silicon for a specific process.
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