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vrkrishn

From class we learned that ASICs were fixed function units that are extremely energy efficient and high performance in regard to the function that they are designed to run. However, I did some more research about why the performance of the FPGA unit is still much better than the CPU, but an order of magnitude worse than the ASIC unit.

FPGA are Field-Programmable Gate Arrays, which essentially are programmable hardware devices. They are optimal in design situations where there is a limited volume of production or in which rapid prototyping is necessary. Often ASIC units require considerable investment to manufacture and design so FPGAs are good for testing environment.

FPGAs consume more power because they tend to have a lower gate utilization as compared to ASIC units. They also rely on memory technology and lookup tables, which don’t offer particularly efficient power or speed. There are many power control methods on ASIC chips that don't work on FPGAs.

Even though both the FPGA and ASIC units are synthesized hardware execution units, the FPGA sacrifices energy efficiency and performance for flexibility and decreased cost of design.

However, the FPGA is still hardware. It has an amazing internal bandwidth and a potential for parallelism and data flow that does not directly map to a CPU implementation.

bxb

A technique commonly used to save power (but highly discouraged in CMU's undergrad RTL design courses) is clock gating. The clock tree in FPGAs are fixed, unlike in ASICs where it is specially built, which enables this technique to be used.