The NOVA microhypervisor combines microkernel and hypervisor functionality and provides an extremely small trusted computing base for user applications and virtual machines running on top of it. The microhypervisor implements a capability-based authorization model and provides basic mechanisms for virtualization, spatial and temporal separation, scheduling, communication, and management of platform resources. The talk will focus on the hypervisor interface and how it can be used by a multi-server environment to manage platform resources, virtual machines, and user applications. After introducing the capability concept and the basic communication mechanisms, more advanced topics such as IOMMU support and real-time scheduling will be discussed.