A control (or virtualization) layer between hardware and the operating system. It allocates resources, reserves resources, and protects resources among (for example) sets of SPEs that may be running under different operating systems.
The Cell Broadband Engine has three operating modes: user, supervisor and hypervisor. The hypervisor performs a meta-supervisor role that allows multiple independent supervisors’ software to run on the same hardware platform.
For example, the hypervisor allows both a real-time operating system and a traditional operating system to run on a single PPE. The PPE can then operate a subset of the SPEs in the Cell Broadband Engine with the real-time operating system, while the other SPEs run under the traditional operating system.