Unisys Corporation

James L Depenning

Roger Lee Gilbertson

Mitchell A Bauman

Michael L Haupt

Penny L Svenkeson

Donald R Kalvestrand

Daniel S Tokoly

Frederick George Fellenser

Matthew D Rench

Maria A Liedman

The current invention provides a system and method for managing requests from one or more requesters to one or more resources. These requests, which may be any of multiple request types, are prioritized using one or more threshold values. Each threshold value is associated with one or more of the request types, and defines the maximum number of requests of the associated types that may be pending to the resources before the threshold is reached. When all associated thresholds have been reached for requests of one or more predetermined request types, an indication is provided to re-issue requests of those types at a later time. A priority scheme is used to allow re-issued requests to systematically gain access to the shared resource to prevent the starvation of any given requester.

System and method for performing conflict resolution and flow control in a multiprocessor system

Poisoning of specific memory locations as a process when a part of a multiprocessor computer system becomes faulty leads to ability to isolate specific data owned by individual failing units even in a shared memory area. Also continuous processing by non-failing units is allowable. A support processor handles non-immediate problems and allows resetting of memory locations formerly owned by failed units.

System and method for fault handling and recovery in a multi-processing system having hardware resources shared between multiple partitions

A request invalidation system for invalidating pending requests within a data processing system is disclosed. According to the system of the preferred embodiment, one or more requesting units may make requests to gain access to one or more shared resources. These requests are stored in a central request storage unit and are processed according to a predetermined priority scheme. Each request includes multiple fields for storing information about the request. Within the data processing system, error indicators are provided to indicate the occurrence of a fault, and to further provide an error indication value that provides information about the nature of the fault. Ones of these error indicators are associated with a respective one of the request fields. According to the current request invalidation system, mode control logic is provided to programmably select one of the request fields as the invalidation field. If any error indicator is asserted that is associated with the selected invalidation field, the error indication value for this error indicator is compared against the invalidation field of all pending requests. In the event a predetermined relationship exists between the two compared values, the associated pending request is discarded without being presented to the requested shared resource. According to one aspect of the invention, the invalidation field is selectable by a scan-set interface that may be dynamically re-programmed during normal system operations. According to another aspect of the invention, ones of the error indicators are each associated with a respective requesting unit or a shared resource. Once an error indicator that is associated with a requesting unit or a shared resource has been asserted, no further requests for that requesting unit or shared resource will be stored within the request storage unit until a reset operation is performed. In one embodiment of the current invalidation system, the system includes logic to generate invalidation requests, which are requests to invalidate one or more pending requests based on an invalidation field and error indication value included in the request. The invalidation system further includes logic for using the invalidation field provided by an invalidation request to override the invalidation field that is programmably selected by the scan-set interface.

Programmable system for invalidating pending requests within a data processing system

A system and method for prioritizing the delivery of information transfer requests using a least-recently-serviced rotational priority technique in a data processing system having one or more requesters to supply the information transfer requests. Active requesters have currently pending information transfer requests, and non-active requesters have no currently pending information transfer requests. Transfer authorization is granted to an information transfer request associated with an active requester that is currently assigned to the highest priority level in a range of priority levels. Each of the active and non-active requesters that have a priority level less than the priority level of the active requester that was granted the transfer have their priority levels incremented, while the non-active requesters having a priority level greater than the priority level of the active requester that was granted the transfer is maintained at its current priority level. The priority level of the active requester that was granted the transfer is then reassigned to the lowest priority level in the range of priority levels.

Method and apparatus for prioritizing delivery of data transfer requests

A system and method for managing the flow of data transfer requests from requesting devices to associated data transfer interconnection circuitry in a data processing system. Data transfers are initiated with data transfer requests that identify a data input queue and data output queue for which the data is to be transferred. The data transfer requests are issued from one or more requesting devices in the system. The data transfer requests are queued at a first queuing level. Within the first queuing level, data transfer requests identifying like data input queues are queued together, yet separate from data transfer requests identifying a different data input queue. Each of the data transfer requests from each of the queues in the first queuing level are transferred to a second queuing level to be queued according to the data output queue identified in the data transfer request. Each queue in the second queuing level stored only those data transfer requests identifying like data output queues. A control signal set is generated for each of the data transfer requests that are output from the second queuing level, and each control signal set identifies the data input queue and the data output queue between which the data is to be transferred. The data from the identified data input queues is transferred to the identified data output queues in response to the corresponding control signal sets.

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Eagan, MN, United States of America

James L Depenning