• System-level power. As already mentioned, it's no longer the processor core and caches, it's the entire system—including interconnects, memory, disks, and networking hardware—that we need to worry about.
• Control stability and determinism. How do we prove the stability of our power-control techniques and verify that they provide a guarantee under all possible conditions? Many industry architects will shy away from complex control systems that might, just once, fail miserably.
• dl/dt noise. Noise margins are thinner than ever, and power-control techniques exacerbate simultaneous switching noise. The excellent work done thus far in this area is overshadowed by the extent of the problem that remains.
• Tools and analysis. Despite many notable efforts, there is an ongoing need for improving the efficacy of architecture-level power-modeling and analysis tools.
• Optimizing for more varied workloads. For instance, many important workloads include a significant system-level software component. Several academic groups have invested significant effort in developing full-system performance and power-modeling environments and have graciously made their tools widely available to the community.