This paper first presents an analysis of the global thermal field in many core processors in deep nanometer (to 16nm) nodes
under power and thermal budget. We show that the thermal field can have significant spatiotemporal non-uniformity along
with high maximum temperature. We propose spatiotemporal power multiplexing as a proactive method to reduce spatial
and temporal temperature gradients. Several power multiplexing policies are evaluated for a 256 core many-core processor
in 16nm nodes which demonstrate that the simple cyclic core-activation can achieve highly uniform thermal field with low
maximum temperature.