1. An on-chip substrate voltage controller comprising means for measuring impact of process variation supply voltage variation
and temperature deviation on circuit performance and means for applying an appropriate substrate bias to adjust chip performance
and power consumption, wherein said means for measuring impact of process variation supply voltage variation and temperature
deviation on circuit performance comprises a multiplexer and at least three separate unconnected chains of interconnected
loaded ring oscillators connected to said multiplexer, wherein each chain is configured such that an output of said chain
is both fed back to an input of said chain as well as provided as an input to said multiplexer, and only the output of each
chain is provided as an input to said multiplexer, wherein said means for measuring impact of process variation supply voltage
variation and temperature deviation on circuit performance further comprises a comparator, wherein an output of said multiplexer
is connected to said comparator, wherein said comparator also receives an output from a PLL, wherein the comparator is configured
to compare the output of said multiplexer to the output of said PLL, wherein said means for applying an appropriate substrate
bias to adjust chip performance and power consumption comprises a controllable voltage regulator, wherein an output of said
comparator is connected to said controllable voltage regulator, wherein said controllable voltage regulator receives a voltage
in as well as the output of said comparator, wherein the voltage in is provided only to said controllable voltage regulator
and not to said comparator, and wherein said controllable voltage regulator is configured to apply the substrate bias depending
on what is received from said comparator.
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