Fixed bus tags for SMP buses

Abstract

According to a first aspect of the present invention, a data processing system is provided that includes a communication network to which multiple devices are coupled. A first of the multiple devices includes a number of requestors (or queues), which are each permanently assigned a respective one of a number of unique tags. In response to a communication request by a requestor within the first device, a tag assigned to the requestor is transmitted on the communication network in conjunction with the requested communication transaction. According to a second aspect of the present invention, a data processing system includes a cache having a cache directory. A status indication indicative of the status of at least one of a plurality of data entries in the cache is stored in the cache directory. In response to receipt of a cache operation request, a determination is made whether to update the status indication. In response to the determination that the status indication is to be updated, the status indication is copied into a shadow register and updated. The status indication is then written back into the cache directory at a later time. The shadow register thus serves as a virtual cache controller queue that dynamically mimics a cache directory entry without functional latency.

Dependencies are inferred from the claim text.