Modern processors are very careful about this, and actively turn off the supply voltage to large parts of the die to prevent extra leakage current. The funny-but-appropriate name for this is "dark silicon" https://en.wikipedia.org/wiki/Dark_silicon
> at 8 nm technology nodes, the amount of dark silicon may reach up to 50–80%
Damn TIL, I never would've expected that. But I guess it makes sense to use a few of the older, larger transistors that don't leak as much to power off a section of the smaller leaky ones while they're not performing any operations.
Hey, keep in mind that things like large caches, neural cores, SIMD units, DSP circuitry all count as dark silicon. The proliferation of these kind of components was predicted 15-20 years ago as a necessary response to the Dennard Scaling breakdown.
Modern processors are very careful about this, and actively turn off the supply voltage to large parts of the die to prevent extra leakage current. The funny-but-appropriate name for this is "dark silicon" https://en.wikipedia.org/wiki/Dark_silicon