voltage island

A voltage island is a physical patch of the chip floorplan deliberately fed a different supply voltage from its neighbours, so each block can run at exactly the voltage it needs and no more. Imagine a city where the hospital gets premium uninterrupted power, the data centre runs at a higher line voltage for speed, and the sleepy suburbs coast on a low economy voltage — each district paying only for the power it truly needs.

This technique, called multi-supply voltage (MSV) design, exploits the V² term in dynamic power: a block that doesn't need to be fast is dropped to a lower voltage to save energy, while a speed-critical block keeps a higher voltage. The trade-off is real-estate and complexity — each island needs its own power grid, its own power straps, and level shifters on every wire that crosses its border. Voltage islands are the physical-design realisation of power domains, and they are the static cousin of DVFS, which instead changes a block's voltage on the fly.