Micro-Partitioning is a form of logical partitioning which was introduced by IBM on systems using the POWER5 processor, and is also referred to as a shared processor partition, and only differs from a dedicated processor partition in the way CPU utilization is configured and managed by the POWER Hypervisor (PHYP) firmware.
All IBM POWER5 and POWER6 systems are partitioned and will run "on top" of the PHYP.
The POWER Hypervisor controls time slicing, management of all hardware interrupts, dynamic movement of resources across multiple operating systems, and dispatching of logical partition workloads.
When a shared processor partition is activated by the PHYP, the logical partition (LPAR) is guaranteed a certain processing capacity, if needed, and a number of virtual processors, based on configuration and current availability.
The processing capacity is drawn from a pool of shared processor resources.