Forward to the Past: An Alternative to Hybrid CPU Design

Hybrid CPUs are a response from industry to the increasingly difficult problem of power management in desktop-class processors. Hybrid CPUs comprise a big/performance core for regular tasks and a small/efficiency core primarily for background OS tasks. Although helpful in managing power, the introduction of two different kinds of cores in such a design significantly complicates the scheduling of applications across cores. It also introduces other issues such as ISA compatibility, OS compatibility, many processor SKUs/configurations and the difficulty with designing/validating two independent cores. We propose to simplify with the use of a single core that is application-aware and adjusts the core and the caches both based on observed IPC within application regions and priority across applications (regular versus background tasks). We show that this simpler design is similarly effective in managing system power and saving energy as the existing hybrid CPU s with two different kinds of cores.