1. A system comprising: a plurality of processors; a partition manager to allocate a first subset of the plurality of processors to a first partition, the first partition to execute first operating system software to manage the first subset of the plurality of processors as resources individually accessible to the first operating system software, the partition manager also to allocate a second subset of the plurality of processors to a second partition, the second partition to execute second operating system software to manage the second subset of processors as resources individually accessible to the second operating system software; wherein at least one of the plurality of processors includes: partitioning logic to support allocation of the first subset of processors to the first partition and the allocation of the second subset of processors to the second partition; and mode logic to reversibly switch operation of at least one of the plurality of processors between a first mode, a second mode and a third mode, wherein the partitioning logic is configurable in the second mode, the partitioning logic is not configurable in the first mode but enabled to maintain and enforce partitioning, the partitioning logic is not configurable in the third mode and not enabled to maintain and enforce partitioning, wherein the mode logic is to switch the operation from the third mode to the second mode responsive to an instruction to request partitioning, and in the second mode the system is to execute at least one of the first operating system software and the second operating system software; and an inter-partition bridge to be managed by the partition manager, the inter-partition bridge to enable the first operating system software to access the second partition, wherein at least one of the plurality of processors includes bridge logic configurable in the second mode to support the management of the inter-partition bridge.