Abstract: While system-directed checkpointing can be implemented in various ways, for example by adding checkpointing support in the memory controller or in the operating system in otherwise standard computers, implementation at the hypervisor level enables the necessary state information to be captured efficiently while providing a number of ancillary advantages over those prior-art methods. This disclosure details procedures for realizing those advantages through relatively minor modifications to normal hypervisor operations. Specifically, by capturing state information in a guest-operating-system-specific manner, any guest operating system can be rolled back independently and resumed without losing either program or input/output (I/O) continuity and without affecting the operation of the other operating systems or their associated applications supported by the same hypervisor.

Abstract: While system-directed checkpointing can be implemented in various ways, for example by adding checkpointing support in the memory controller or in the operating system in otherwise standard computers, implementation at the hypervisor level enables the necessary state information to be captured efficiently while providing a number of ancillary advantages over those prior-art methods. This disclosure details procedures for realizing those advantages through relatively minor modifications to normal hypervisor operations. Specifically, by capturing state information in a guest-operating-system-specific manner, any guest operating system can be rolled back independently and resumed without losing either program or input/output (I/O) continuity and without affecting the operation of the other operating systems or their associated applications supported by the same hypervisor.

Abstract: System-directed checkpointing is enabled in otherwise standard computers through relatively straightforward augmentations to the computer's memory controller hub.

Abstract: System-directed checkpointing is enabled in otherwise standard computers through relatively straightforward augmentations to the computer's memory controller hub.

Abstract: A distributed computer system having a plurality of digital computer systems interconnected by a bus. Each digital computer system runs one or more programs. When it receives a command directed to a system device or a program, it determines whether it can fulfill the command. If not, it determines which one of the other digital computer systems can fulfill the command based upon retaining information stored locally and forwards the command to the other digital computer system.

Abstract: A method of assigning priorities and resolving bus contention in a distributed computer system is disclosed. Each system node is assigned an identifier. Priorities are reassigned at each change in bus access such that the node that most recently had access to the bus is assigned the lowest priority with the node having the next identifier in sequence being assigned the highest priority and all other nodes assigned priority in accordance with their identifier's position in the sequence. The identifiers are logically treated as organized in a circular fashion such that the lowest node identifier is considered to come next in the sequence after the highest node identifier.

Abstract: System-directed checkpointing is enabled in otherwise standard computers through relatively straightforward augmentations to the computer's memory controller hub.