Bit Serializing a Microprocessor for Ultra-low-power

Many emerging sensor applications are powered by energy harvesters that impose strict power constraints. These applications often do not require high performance or energy efficiency. We explore a technique for minimizing power of a microprocessor for power constrained applications: bit serial computing. Bit serial computing promises power benefits up to the data width for fully bit serializable logic. We perform a best-effort bit serialization of the openMSP430 microprocessor without making instruction set architecture (ISA) modifications. Although it is very challenging to serialize much of the logic in the microprocessor, we show that power benefits of serialization exceed 42% when the serial and parallel designs synthesized for their maximum operating frequency are running at a low duty cycle. Benefits are expected to be higher when ISA modifications are allowed.