Abstract: An apparatus comprises processing circuitry to process data access operations specifying a virtual address of data to be loaded from or stored to a data store, and proxy identifier determining circuitry to determine a proxy identifier for a data access operation to be processed by the data access circuitry, the proxy identifier having fewer bits than a physical address corresponding to the virtual address specified by the data access operation. The processing circuitry comprises at least one buffer to buffer information (including the proxy identifier) associated with one or more pending data access operations awaiting processing. Address translation circuitry determines the physical address corresponding to the virtual address specified for a data access operation after that data access operation has progressed beyond said at least one buffer.

Abstract: An interconnect is provided that has a plurality of nodes, and a ring network to which each of the nodes is connected to allow packets to be transmitted between nodes. For an ordered sequence of packets one of the nodes is arranged as a source node to add each packet of the ordered sequence on to the ring network, and another of the nodes is arranged as a destination node to remove each packet of the ordered sequence from the ring network. The source node is enabled to add a packet of the ordered sequence on to the ring network without waiting for a previously added packet of the ordered sequence to be removed from the ring network by the destination node.

Abstract: An apparatus for handling resets corresponding to multiple reset domains comprises a transport network interconnecting elements to enable data to be transferred from one element to another, ingress circuitry to couple elements to the transport network, and egress circuitry to couple the transport network to the elements. The ingress circuitry couples source elements to the transport network, and is responsive to receiving data from a source element to generate at least one transport packet in order to send that data over the transport network. Each transport packet comprises a reset domain indicator indicative of the reset domain in which the source element operates. The egress circuitry couples the transport network to destination elements and, whilst a reset of a particular reset domain is asserted, discards transport packets for which the reset domain indicator indicates the particular reset domain.

Abstract: An apparatus and method are provided for managing a cache. The cache is arranged to comprise a plurality of cache sections, where each cache section is powered independently of the other cache sections in the plurality of cache sections, and the apparatus has power control circuitry to control power to each of the cache sections. The power control circuitry is responsive to a trigger condition indicative of an ability to operate the cache in a power saving mode, to perform a latency evaluation process to determine a latency indication for each of the cache sections, and to control which of a subset of the cache sections to power off in dependence on the latency indication. This can allow the power consumption savings realised by turning off one or more cache sections to be optimised to take into account the current system state.

Abstract: Circuitry comprises a data store to hold status data indicating a status of a first set of one or more devices connected to the interconnect circuitry; and control circuitry, responsive to initiation of a data handling transaction, to generate recovery data indicative of an initial state of the status data and to predict a predicted revised state of the status data applicable to resolution of the data handling transaction; the control circuitry being configured to change the status data to the predicted revised state in response to initiation of the transaction and before resolution of the transaction, and in response to a request to access the status data between the change of the status data to the predicted revised state and the resolution of the transaction, to provide access to the initial state of the status data, using the recovery data.

Abstract: An interconnect, and method of operation of such an interconnect, are disclosed. The interconnect has a plurality of nodes, and a routing network via which information is routed between the plurality of nodes. The plurality of nodes comprises at least one slave node used to couple master devices to the interconnect, at least one master node used to couple slave devices to the interconnect, and at least one control node. Each control node is responsive to a slave node request received via the routing network from a slave node, to perform an operation to service the slave node request and, when a propagation condition is present, to issue a control node request via the routing network to a chosen master node in order to service the slave node request. The chosen master node processes the control node request in order to generate a master node response, and treats as a default destination for the master node response the control node that issued the control node request.

Abstract: Aspects of the present disclosure relate to an interconnect comprising an interface to couple to a master device, the interface comprising buffer storage. The interface is configured to receive a request from the master device for data comprising a plurality of data blocks, the master device requiring the data blocks in a defined order. A data collator is configured to: receive the request; issue a data pull request to cause the interface to allocate buffer space in the buffer storage for buffering the requested data; and responsive to receiving a confirmation that the buffer space is allocated, provide the requested data to the buffer storage. The interface is configured to employ the buffer storage to enable re-ordering of the plurality of data blocks of the requested data, prior to outputting the plurality of data blocks to the master device; and output the plurality of data blocks to the master device in the defined order.

Abstract: At least one processor core has debug and non-debug modes of operation. Debug control circuitry controls operation of the at least one processor core when in the debug mode. On power up of a given processor core, the core checks a debug status value stored in a debug status storage element. When the debug status value has a first value, a debug connect sequence of messages is exchanged with the debug control circuitry over a debug interface to determine whether the given processor core should operate in the debug mode or the non-debug mode, and the debug status value is set to a second value when it is determined that the given processor core should operate in the non-debug mode. When the debug status value has the second value, the given processor core omits initiating the debug connect sequence and determines that it should operate in the non-debug mode.

Abstract: An interconnect is provided that has a plurality of nodes, and a ring network to which each of the nodes is connected to allow packets to be transmitted between nodes. For an ordered sequence of packets one of the nodes is arranged as a source node to add each packet of the ordered sequence on to the ring network, and another of the nodes is arranged as a destination node to remove each packet of the ordered sequence from the ring network. The source node is enabled to add a packet of the ordered sequence on to the ring network without waiting for a previously added packet of the ordered sequence to be removed from the ring network by the destination node.

Abstract: An interconnect, and method of operation of such an interconnect, are disclosed. The interconnect has a plurality of nodes, and a routing network via which information is routed between the plurality of nodes. The plurality of nodes comprises at least one slave node used to couple master devices to the interconnect, at least one master node used to couple slave devices to the interconnect, and at least one control node. Each control node is responsive to a slave node request received via the routing network from a slave node, to perform an operation to service the slave node request and, when a propagation condition is present, to issue a control node request via the routing network to a chosen master node in order to service the slave node request. The chosen master node processes the control node request in order to generate a master node response, and treats as a default destination for the master node response the control node that issued the control node request.

Abstract: A first event source generates a first indication of a first event which has occurred in the first event source, the first indication being one of a predefined set of indications corresponding to a plurality of event types. A second event source generates a second indication of a second event which has occurred in the second event source, the second indication being one of the predefined set of indications corresponding to the plurality of event types. First event selection circuitry responds to the first indication matching a selected event type of the plurality of event types to generate a first count signal and second event selection circuitry responds to the second indication matching the selected event type of the plurality of event types to generate a second count signal. Count circuitry increments a counter in response to either the first count signal or the second count signal.

Abstract: An apparatus and method are provided for supporting multiple cache features. The apparatus provides cache storage comprising a plurality of cache ways and organised as a plurality of ways groups, where each way group comprises multiple cache ways from the plurality of cache ways. First cache feature circuitry is provided to implement a first cache feature that is applied to the way groups, and second cache feature circuitry is provided to implement a second cache feature that is applied to the way groups. Way group control circuitry is then arranged to provide a first mapping defining which cache ways belong to each way group when the first cache feature is applied to the way groups, and a second mapping defining which cache ways belong to each way group when the second cache feature is applied to the way groups.

Abstract: At least one processor core has debug and non-debug modes of operation. Debug control circuitry controls operation of the at least one processor core when in the debug mode. On power up of a given processor core, the core checks a debug status value stored in a debug status storage element. When the debug status value has a first value, a debug connect sequence of messages is exchanged with the debug control circuitry over a debug interface to determine whether the given processor core should operate in the debug mode or the non-debug mode, and the debug status value is set to a second value when it is determined that the given processor core should operate in the non-debug mode. When the debug status value has the second value, the given processor core omits initiating the debug connect sequence and determines that it should operate in the non-debug mode.

Abstract: A data processing system (2) incorporates a first exclusive cache memory (8, 10) and a second exclusive cache memory (14). A snoop filter (18) located together with the second exclusive cache memory on one side of the communication interface (12) serves to track entries within the first exclusive cache memory. The snoop filter includes retention data storage circuitry to store retention data for controlling retention of cache entries within the second exclusive cache memory. Retention data transfer circuitry (20) serves to transfer the retention data to and from the retention data storage circuitry within the snoop filter and the second cache memory as the cache entries concerned are transferred between the second exclusive cache memory and the first exclusive cache memory.

Abstract: A ring interconnect system comprises a plurality of nodes. Each node is connected to two other nodes to form a ring interconnect. Every pair of nodes is connected by an inter-node path for that pair of nodes distinct from the ring interconnect. Each of the nodes comprises a message buffer to buffer messages received from at least one device associated with the node. Each of the nodes also comprises activity level circuitry to transmit an activity indication, when a number of the messages in the message buffer is equal to or above a threshold, to each other node of the plurality of nodes via the respective inter-node paths. Each of the nodes also comprises arbitrator circuitry to receive the activity indications from each other node and from the activity level circuitry, and to allow ingress of a message from the message buffer onto the ring interconnect in dependence on the activity indications.

Abstract: A first event source generates a first indication of a first event which has occurred in the first event source, the first indication being one of a predefined set of indications corresponding to a plurality of event types. A second event source generates a second indication of a second event which has occurred in the second event source, the second indication being one of the predefined set of indications corresponding to the plurality of event types. First event selection circuitry responds to the first indication matching a selected event type of the plurality of event types to generate a first count signal and second event selection circuitry responds to the second indication matching the selected event type of the plurality of event types to generate a second count signal. Count circuitry increments a counter in response to either the first count signal or the second count signal.

Abstract: An apparatus (300) for processing data comprises a plurality of memory access request sources (102,104) which generate memory access requests. Each of the memory access request sources has a local memory (106,108), and the apparatus also includes a shared memory (110). When the memory access requests are atomic memory access requests, contention may arise over common data. When this occurs, the present technique triggers a switch of processing data in the local memory of a memory access request source to processing data in the shared memory.

Abstract: An apparatus and method are provided for operating a virtually indexed, physically tagged cache. The apparatus has processing circuitry for performing data processing operations on data, and a virtually indexed, physically tagged cache for storing data for access by the processing circuitry. The cache is accessed using a virtual address portion of a virtual address in order to identify a number of cache entries, and then physical address portions stored in those cache entries are compared with the physical address derived from the virtual address in order to detect whether a hit condition exists.

Abstract: An apparatus includes control circuitry configured to receive a first N-bit count value in a first domain, and to determine an M-bit increment indicating value based on the first N-bit count value and a reference value, where M<N. Boundary circuitry is configured to provide the M-bit increment indicating value to a second domain. In the second domain, updating circuitry configured to update a second N-bit count value based on an increment represented by the M-bit increment indicating value provided by the boundary circuitry.

Abstract: There is provided a data processing apparatus comprising: processing circuitry to speculatively execute an instruction referencing a virtual address. Lookup circuitry receives the virtual address from the processing circuitry. The lookup circuitry comprises storage circuitry to store at least one virtual address and page walking circuitry to perform a page walk on further storage circuitry, in dependence on the virtual address being unlisted by the storage circuitry, to determine whether a correspondence between a physical address and the virtual address exists. The lookup circuitry signals an error when the correspondence cannot be found and, in response to the error being signaled, the storage circuitry stores an entry comprising the virtual address.