Globally asynchronous locally synchronous (GALS), in electronics, is an architecture for designing electronic circuits that addresses the problem of safe and reliable data transfer between independent clock domains.
A GALS circuit consists of a set of locally synchronous modules communicating with each other via asynchronous wrappers.
The CMOS circuit (logic gates) requires relatively large supply current when changing state from 0 to 1.
Therefore, large spikes on supply current occur at active clock edges.
Generally each CPU in such an asynchronous array of simple processors has its own independent oscillator.