Integrated CPU Cache Power Management in Multiple Clock Domain Processors

Abstract

Multiple clock domain (MCD) chip design addresses the problem of increasing clock skew in different chip units. Importantly, MCD design offers an opportunity for fine grain power/energy management of the components in each clock domain with dynamic voltage scaling (DVS). In this paper, we propose and evaluate a novel integrated DVS approach to synergistically manage the energy of chip components in different clock domains. We focus on embedded processors where core and L2 cache domains are the major energy consumers. We propose a policy that adapts clock speed and voltage in both domains based on each domain’s workload and the workload experienced by the other domain. In our approach, the DVS policy detects and accounts for the effect of inter-domain interactions. Based on the interaction between the two domains, we select an appropriate clock speed and voltage that optimizes the energy of the entire chip. For the Mibench benchmarks, our policy achieves an average improvement over no-power-management of 15.5% in energy-delay product and 19% in energy savings. In comparison to a traditional DVS policy for MCD design that manages domains independently, our policy achieves an 3.5% average improvement in energy-delay and 4% less energy, with a negligible 1% decrease in performance. We also show that an integrated DVS policy for MCD design with two domains is more energy efficient for simple embedded processors than high-end ones.