5.7 A graphics execution core in 22nm CMOS featuring adaptive clocking, selective boosting and state-retentive sleep

The demand for high-performance graphics capability even in extremely power-constrained platforms such as smartphones and tablets requires circuit techniques that scale from efficient operation at low voltage to high performance when needed. It is well known that energy efficiency improves as supply voltage is scaled down, reaching a maximum near the device threshold voltage where switching energy savings from voltage reduction is balanced by increased leakage energy from frequency loss. Achieving this voltage reduction, however, requires techniques that address intrinsic V
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limitations in arrays (SRAM, register file arrays, ROMs), voltage droop guardband reduction in logic, as well as techniques for reducing leakage energy, which can dominate at low voltage. It is important that these techniques, while providing energy-efficient operation at low voltage, do not impact the high-performance mode, which is also critical for graphics workloads.