> Instead of adapting an existing microcontroller architecture to plastic, Kumar’s team started from scratch to create a design called Flexicore. “Yield goes down very quickly as you increase gate count,” says Kumar. Knowing that, they came up with a design meant to minimize the number of gates needed. Using 4-bit and 8-bit logic instead of 16-bit or 32-bit helped. As did separating the memory that stores instructions from the memory that stores data. But they also cut down on the number and complexity of the instructions the processor is capable of executing.
> The team further simplified, by designing the processor so it executes an instruction in a single clock cycle instead of the mulit-step pipelines of today’s CPUs. Then they designed logic that implements those instructions by reusing parts, further reducing the gate count. “In general, we were able to simplify the design of FlexiCores by tailoring them to the needs of flexible applications, which tend to be computationally simple,” says Nathaniel Bleier, Kumar's student.
> All of this resulted in a 5.6 square millimeter 4-bit FlexiCore made up of just 2,104 semiconductor devices (about the same as the number of transistors in an Intel 4004 from 1971) versus some 56,340 devices for PlasticARM.