Abstract: An apparatus comprises transaction handling circuitry to issue memory access transactions, each memory access transaction specifying an epoch identifier indicative of a current epoch in which the memory access transaction is issued; transaction tracking circuitry to track, for each of at least two epochs, a number of outstanding memory access transactions issued in that epoch; barrier termination circuitry to signal completion of a barrier termination command when the transaction tracking circuitry indicates that there are no outstanding memory access transactions remaining which were issued in one or more epochs preceding a barrier point; and epoch changing circuitry to change the current epoch to a next epoch, in response to a barrier point signal representing said barrier point. This helps to reduce the circuit area overhead for tracking completion of memory access transactions preceding a barrier point.

Abstract: Apparatus comprises address translation circuitry configured to access translation data defining a set of memory address translations; transaction handling circuitry to receive translation transactions and to receive invalidation transactions, each translation transaction defining one or more input memory addresses in an input memory address space to be translated to respective output memory addresses in an output memory address space, in which the transaction handling circuitry is configured to control the address translation circuitry to provide the output memory address as a translation response; in which each invalidation transaction defines at least a partial invalidation of the translation data; transaction tracking circuitry to associate an invalidation epoch, of a set of at least two invalidation epochs, with each translation transaction and with each invalidation transaction; and invalidation circuitry to store data defining a given invalidation transaction and, for translation transactions having th

Abstract: Apparatus comprises address translation circuitry configured to access translation data defining a set of memory address translations; transaction handling circuitry to receive translation transactions and to receive invalidation transactions, each translation transaction defining one or more input memory addresses in an input memory address space to be translated to respective output memory addresses in an output memory address space, in which the transaction handling circuitry is configured to control the address translation circuitry to provide the output memory address as a translation response; in which each invalidation transaction defines at least a partial invalidation of the translation data; transaction tracking circuitry to associate an invalidation epoch, of a set of at least two invalidation epochs, with each translation transaction and with each invalidation transaction; and invalidation circuitry to store data defining a given invalidation transaction and, for translation transactions having th

Abstract: An apparatus comprises transaction handling circuitry to issue memory access transactions, each memory access transaction specifying an epoch identifier indicative of a current epoch in which the memory access transaction is issued; transaction tracking circuitry to track, for each of at least two epochs, a number of outstanding memory access transactions issued in that epoch; barrier termination circuitry to signal completion of a barrier termination command when the transaction tracking circuitry indicates that there are no outstanding memory access transactions remaining which were issued in one or more epochs preceding a barrier point; and epoch changing circuitry to change the current epoch to a next epoch, in response to a barrier point signal representing said barrier point. This helps to reduce the circuit area overhead for tracking completion of memory access transactions preceding a barrier point.

Abstract: Arbitrating circuitry arbitrates between a plurality of inputs and a selection of at least one of said plurality of inputs. The arbitrating circuitry includes an array of interconnected arbiter devices operating with respect to a set of Q inputs. The array comprises M sub-levels with at least a first sub-level having T arbiter devices each operating with respect to U inputs, where Q=UM and Q=TU. For each sub-level other than a first sub-level, each arbiter device in a sub-level receives as input requests signals indicating an arbitration outcome for two or more arbiter devices in a preceding sub-level and arbitrates between those input requests.

Abstract: Arbitrating circuitry arbitrates between a plurality of inputs and a selection of at least one of said plurality of inputs. The arbitrating circuitry includes an array of interconnected arbiter devices operating with respect to a set of Q inputs. The array comprises M sub-levels with at least a first sub-level having T arbiter devices each operating with respect to U inputs, where Q=UM and Q=TU. For each sub-level other than a first sub-level, each arbiter device in a sub-level receives as input requests signals indicating an arbitration outcome for two or more arbiter devices in a preceding sub-level and arbitrates between those input requests.

Abstract: Arbitrating and multiplexing circuitry for performing an arbitration between a plurality of inputs and a selection of at least one of said plurality of inputs to provide an output comprises arbitrating tree circuitry having X arbitrating levels, where X is an integer greater than one; and multiplexing tree circuitry having Y multiplexing levels, where Y is an integer greater than one; wherein (i) said Y multiplexing levels comprise a first set of said multiplexing levels upstream of a second set of said multiplexing levels; (ii) said first set of said multiplexing levels is configured to operate in parallel with at least some of said X arbitrating levels, whereby said first set of multiplexing levels is configured to perform a partial selection in parallel with said arbitration performed by said X arbitrating levels; and (iii) said second set of said multiplexing levels is configured to operate in series with said X arbitrating levels, whereby said second set of multiplexing levels completes said selection to

Abstract: An interconnect, and method of operation of an interconnect, are provided for connecting a plurality of master devices and a plurality of slave devices. Hazard management circuitry is used to serialize transactions to overlapping addresses. In addition, gating circuitry ensures ordered write observation (OWO) behavior at an interface to one or more of the master devices, the gating circuitry receiving write address transfers of write transactions and performing a gating operation to gate onward propagation of the write address transfers to the slave devices in order to ensure the OWO behavior. The gating circuitry performs the gating operation under control of the hazard management circuitry. Hence, for write transactions that are subjected to hazard checking by the hazard management circuitry, this removes the need to implement any other processes to specifically manage OWO behavior for those write transactions.

Abstract: Interconnect circuitry for connecting transaction masters to transaction slaves includes response modification circuitry. The response modification circuitry includes shortlist buffer circuitry storing identification for modification target transaction responses. The response modification circuitry uses this identification data to identify among a stream of transaction responses in transit a modification target transaction response. The response modification circuitry then serves to form a modified transaction response to be sent in place of the modification target transaction response to the transaction master.

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-serialization 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: Arbitrating and multiplexing circuitry for performing an arbitration between a plurality of inputs and a selection of at least one of said plurality of inputs to provide an output comprises arbitrating tree circuitry having X arbitrating levels, where X is an integer greater than one; and multiplexing tree circuitry having Y multiplexing levels, where Y is an integer greater than one; wherein (i) said Y multiplexing levels comprise a first set of said multiplexing levels upstream of a second set of said multiplexing levels; (ii) said first set of said multiplexing levels is configured to operate in parallel with at least some of said X arbitrating levels, whereby said first set of multiplexing levels is configured to perform a partial selection in parallel with said arbitration performed by said X arbitrating levels; and (iii) said second set of said multiplexing levels is configured to operate in series with said X arbitrating levels, whereby said second set of multiplexing levels completes said selection to

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: Interconnect circuitry is configured to provide data routes via which at least one initiator device may access at least one recipient device. The circuitry including: at least one input for receiving transaction requests from at least one initiator device; at least one output for outputting transaction requests to the at least one recipient device; and at least one path for transmitting transaction requests between at least one input and at least one output. Also includes is control circuitry for routing the received transaction requests from at least one input to at least one output and responds to a barrier transaction request to maintain an ordering of at least some transaction requests with respect to said barrier transaction request within a stream of transaction requests passing along one of said at least one paths. Barrier transaction requests include an indicator of transaction requests whose ordering is to be maintained.

Abstract: An interconnect, and method of operation of an interconnect, are provided for connecting a plurality of master devices and a plurality of slave devices. Hazard management circuitry is used to serialise transactions to overlapping addresses. In addition, gating circuitry ensures ordered write observation (OWO) behaviour at an interface to one or more of the master devices, the gating circuitry receiving write address transfers of write transactions and performing a gating operation to gate onward propagation of the write address transfers to the slave devices in order to ensure the OWO behaviour. The gating circuitry performs the gating operation under control of the hazard management circuitry. Hence, for write transactions that are subjected to hazard checking by the hazard management circuitry, this removes the need to implement any other processes to specifically manage OWO behaviour for those write transactions.

Abstract: Interconnect circuitry 10 for connecting transaction masters 4, 6, 8 to transaction slaves 12, 14 includes response modification circuitry 18. The response modification circuitry includes shortlist buffer circuitry 28 storing identification for modification target transaction responses. The response modification circuitry 18 uses this identification data to identify among a stream of transaction responses in transit a modification target transaction response. The response modification circuitry 18 then serves to form a modified transaction response to be sent in place of the modification target transaction response to the transaction master 4, 6, 8.

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: Interconnect circuitry is configured to provide data routes via which at least one initiator device may access at least one recipient device, the circuitry including at least one input for receiving transaction requests; at least one output for outputting transaction requests; at least one path for transmitting the transaction requests between the input and the output. Control circuitry routes received transaction requests from the input to the output in response to a barrier transaction request. An ordering of at least some transaction requests is maintained with respect to the barrier transaction request within a stream of transaction requests passing along one of the at least one paths, by not allowing reordering of at least some of the transactions requests. The control circuitry includes a response signal generator, the response signal generator is responsive to receipt of the barrier transaction request to issue a response signal.

Abstract: Interconnect circuitry for a data processing apparatus is disclosed. The interconnect circuitry is configured to provide data routes via which at least one initiator device may access at least one recipient device.

Abstract: Interconnect circuitry is configured to provide data routes via which at least one initiator device may access at least one recipient device. The circuitry including: at least one input for receiving transaction requests from at least one initiator device; at least one output for outputting transaction requests to the at least one recipient device; and at least one path for transmitting transaction requests between at least one input and at least one output. Also includes is control circuitry for routing the received transaction requests from at least one input to at least one output and responds to a barrier transaction request to maintain an ordering of at least some transaction requests with respect to said barrier transaction request within a stream of transaction requests passing along one of said at least one paths. Barrier transaction requests include an indicator of transaction requests whose ordering is to be maintained.