Abstract:
An interconnect has coherency control circuitry for performing coherency control operations and a snoop filter for identifying which devices coupled to the interconnect have cached data from a given address. When an address is looked up in the snoop filter and misses, and there is no spare snoop filter entry available, then the snoop filter selects a victim entry corresponding to a victim address, and issues an invalidate transaction for invalidating locally cached copies of the data identified by the victim. The coherency control circuitry for performing coherency checking operations for data access transactions is reused for performing coherency control operations for the invalidate transaction issued by the snoop filter. This greatly reduces the circuitry complexity of the snoop filter.
Abstract:
A system-on-check integrated circuit 2 includes interconnect circuitry 4 connecting a plurality of transaction sources to a plurality of transaction destinations. The interconnect circuitry 4 includes a reorder buffer for buffering access transactions and hazard checking circuitry 46, 48, 50, 52 for performing hazard checks, such as point-of-serialisation checks and identifier reuse checks. Check suppression circuitry 62, 64, 66, 68 serves to suppress one or more hazard checks depending upon one or more state variables that themselves depend upon access transactions other than the access transaction for which the hazard checking is or is not to be suppressed. As an example, hazard checking may be suppressed if it is known that there are no other access transactions currently buffered within the reorder buffer 26 or alternatively no other access transactions from the same transaction source buffered within the reorder buffer 26.
Abstract:
A system-on-chip integrated circuit 2 includes interconnect circuitry 4 for communicating transactions between transaction sources and transaction destinations. A reorder buffer 26 serves to buffer and permit reordering of access transactions received from the transaction sources. Processing circuitry performs processing operations in parallel upon a given access transaction taken from the reorder buffer. Hazard detection and repair circuitry serves to detect an ordering hazard arising between the processing operations and if necessary cancel and repeat that processing operation. The access transactions and the reorder buffer are such that access transactions other than the access transaction for which a hazard has been detected may proceed independently of the necessity to cancel and repair that transaction thereby reducing the cost associated with cancelling and repair.