Low power branch prediction for embedded application processors

Modern embedded processors used in media and communication portable devices are now required to execute complex applications and their performance requirements are getting close to the demands of general purpose processors. The performance-per-Watt ratio is an extremely important measure in portable devices because of their limited power capacity. Branch predictors, and especially the BTB, are among the largest on-chip SRAM structures (after caches), and therefore are primary contributors to the total system power. We propose a novel micro-architectural method referred to as Shifted-Index BTB with a Set-Buffer, which reduces both dynamic and static power. Extensive simulations show that up to 80% reduction in dynamic power is achieved at the cost of up to 0.64% system slowdown. 58% reduction is static power is also achieved by applying low-leakage power techniques that mesh well with the Set-Buffer design.