In a programmable SoC (system-on-a-chip) integrated circuit device, a
method for optimizing power efficiency for a requested device
functionality. The method includes determining a requested device
functionality, and in response to the requested device functionality,
turning on power for a selected one or more power domains out of a
plurality of power domains included within the integrated circuit device.
Each of the power domains has its own respective voltage rail to obtain
power. The method further includes turning on one or more power islands
out of a plurality of power islands included within the integrated
circuit device. The requested device functionality is then implemented
using one or more functional blocks wherein each functional block is
configured to provide a specific device functionality.