Abstract: A coherent memory fabric includes a plurality of coherent master controllers and a coherent slave controller. The plurality of coherent master controllers each include a response data buffer. The coherent slave controller is coupled to the plurality of coherent master controllers. The coherent slave controller, responsive to determining a selected coherent block read command is guaranteed to have only one data response, sends a target request globally ordered message to the selected coherent master controller and transmits responsive data. The selected coherent master controller, responsive to receiving the target request globally ordered message, blocks any coherent probes to an address associated with the selected coherent block read command until receipt of the responsive data is acknowledged by a requesting client.

Abstract: Systems, apparatuses, and methods for maintaining a region-based cache directory are disclosed. A system includes multiple processing nodes, with each processing node including a cache subsystem. The system also includes a cache directory to help manage cache coherency among the different cache subsystems of the system. In order to reduce the number of entries in the cache directory, the cache directory tracks coherency on a region basis rather than on a cache line basis, wherein a region includes multiple cache lines. Accordingly, the system includes a region-based cache directory to track regions which have at least one cache line cached in any cache subsystem in the system. The cache directory includes a reference count in each entry to track the aggregate number of cache lines that are cached per region. If a reference count of a given entry goes to zero, the cache directory reclaims the given entry.

Abstract: A coherent memory fabric includes a plurality of coherent master controllers and a coherent slave controller. The plurality of coherent master controllers each include a response data buffer. The coherent slave controller is coupled to the plurality of coherent master controllers. The coherent slave controller, responsive to determining a selected coherent block read command is guaranteed to have only one data response, sends a target request globally ordered message to the selected coherent master controller and transmits responsive data. The selected coherent master controller, responsive to receiving the target request globally ordered message, blocks any coherent probes to an address associated with the selected coherent block read command until receipt of the responsive data is acknowledged by a requesting client.

Abstract: A computing system may implement a low priority arbitration interrupt method that includes receiving a message signaled interrupt (MSI) message from an input output hub (I/O hub) transmitted over an interconnect fabric, selecting a processor to interrupt from a cluster of processors based on arbitration parameters, and communicating an interrupt service routine to the selected processor, wherein the I/O hub and the cluster of processors are located within a common domain.

Abstract: A computing system may implement a low priority arbitration interrupt method that includes receiving a message signaled interrupt (MSI) message from an input output hub (I/O hub) transmitted over an interconnect fabric, selecting a processor to interrupt from a cluster of processors based on arbitration parameters, and communicating an interrupt service routine to the selected processor, wherein the I/O hub and the cluster of processors are located within a common domain.

Abstract: A method of operating a processing unit includes storing a first copy of a first interrupt control value in a cache device of the processing unit, receiving from an interrupt controller a first interrupt message transmitted via an interconnect fabric, where the first interrupt message includes a second copy of the first interrupt control value, and if the first copy matches the second copy, servicing an interrupt specified in the first interrupt message.

Abstract: A method of operating a processing unit includes storing a first copy of a first interrupt control value in a cache device of the processing unit, receiving from an interrupt controller a first interrupt message transmitted via an interconnect fabric, where the first interrupt message includes a second copy of the first interrupt control value, and if the first copy matches the second copy, servicing an interrupt specified in the first interrupt message.

Abstract: Systems, apparatuses, and methods for routing interrupts on a coherency probe network are disclosed. A computing system includes a plurality of processing nodes, a coherency probe network, and one or more control units. The coherency probe network carries coherency probe messages between coherent agents. Interrupts that are detected by a control unit are converted into messages that are compatible with coherency probe messages and then routed to a target destination via the coherency probe network. Interrupts are generated with a first encoding while coherency probe messages have a second encoding. Cache subsystems determine whether a message received via the coherency probe network is an interrupt message or a coherency probe message based on an encoding embedded in the received message. Interrupt messages are routed to interrupt controller(s) while coherency probe messages are processed in accordance with a coherence probe action field embedded in the message.

Abstract: Systems, apparatuses, and methods for reducing chiplet interrupt latency are disclosed. A system includes one or more processing nodes, one or more memory devices, a communication fabric coupled to the processing unit(s) and memory device(s) via link interfaces, and a power management unit. The power management unit manages the power states of the various components and the link interfaces of the system. If the power management unit detects a request to wake up a given component, and the link interface to the given component is powered down, then the power management unit sends an out-of-band signal to wake up the given component in parallel with powering up the link interface. Also, when multiple link interfaces need to be powered up, the power management unit powers up the multiple link interfaces in an order which complies with voltage regulator load-step requirements while minimizing the latency of pending operations.

Abstract: Systems, apparatuses, and methods for maintaining a region-based cache directory are disclosed. A system includes multiple processing nodes, with each processing node including a cache subsystem. The system also includes a cache directory to help manage cache coherency among the different cache subsystems of the system. In order to reduce the number of entries in the cache directory, the cache directory tracks coherency on a region basis rather than on a cache line basis, wherein a region includes multiple cache lines. Accordingly, the system includes a region-based cache directory to track regions which have at least one cache line cached in any cache subsystem in the system. The cache directory includes a reference count in each entry to track the aggregate number of cache lines that are cached per region. If a reference count of a given entry goes to zero, the cache directory reclaims the given entry.

Abstract: Systems, apparatuses, and methods for routing interrupts on a coherency probe network are disclosed. A computing system includes a plurality of processing nodes, a coherency probe network, and one or more control units. The coherency probe network carries coherency probe messages between coherent agents. Interrupts that are detected by a control unit are converted into messages that are compatible with coherency probe messages and then routed to a target destination via the coherency probe network. Interrupts are generated with a first encoding while coherency probe messages have a second encoding. Cache subsystems determine whether a message received via the coherency probe network is an interrupt message or a coherency probe message based on an encoding embedded in the received message. Interrupt messages are routed to interrupt controller(s) while coherency probe messages are processed in accordance with a coherence probe action field embedded in the message.

Abstract: A system for automatically discovering fabric topology includes at least one or more processing units, one or more memory devices, a security processor, and a communication fabric with an unknown topology coupled to the processing unit(s), memory device(s), and security processor. The security processor queries each component of the fabric to retrieve various attributes associated with the component. The security processor utilizes the retrieved attributes to create a network graph of the topology of the components within the fabric. The security processor generates routing tables from the network graph and programs the routing tables into the fabric components. Then, the fabric components utilize the routing tables to determine how to route incoming packets.

Abstract: Systems, apparatuses, and methods for maintaining a region-based cache directory are disclosed. A system includes multiple processing nodes, with each processing node including a cache subsystem. The system also includes a cache directory to help manage cache coherency among the different cache subsystems of the system. In order to reduce the number of entries in the cache directory, the cache directory tracks coherency on a region basis rather than on a cache line basis, wherein a region includes multiple cache lines. Accordingly, the system includes a region-based cache directory to track regions which have at least one cache line cached in any cache subsystem in the system. The cache directory includes a reference count in each entry to track the aggregate number of cache lines that are cached per region. If a reference count of a given entry goes to zero, the cache directory reclaims the given entry.

Abstract: Systems, apparatuses, and methods for reducing chiplet interrupt latency are disclosed. A system includes one or more processing nodes, one or more memory devices, a communication fabric coupled to the processing unit(s) and memory device(s) via link interfaces, and a power management unit. The power management unit manages the power states of the various components and the link interfaces of the system. If the power management unit detects a request to wake up a given component, and the link interface to the given component is powered down, then the power management unit sends an out-of-band signal to wake up the given component in parallel with powering up the link interface. Also, when multiple link interfaces need to be powered up, the power management unit powers up the multiple link interfaces in an order which complies with voltage regulator load-step requirements while minimizing the latency of pending operations.

Abstract: Systems, apparatuses, and methods for dynamic buffer management in multi-client token flow control routers are disclosed. A system includes at least one or more processing units, a memory, and a communication fabric with a plurality of routers coupled to the processing unit(s) and the memory. A router servicing multiple active clients allocates a first number of tokens to each active client. The first number of tokens is less than a second number of tokens needed to saturate the bandwidth of each client to the router. The router also allocates a third number of tokens to a free pool, with tokens from the free pool being dynamically allocated to different clients. The third number of tokens is equal to the difference between the second number of tokens and the first number of tokens. An advantage of this approach is reducing the amount of buffer space needed at the router.

Abstract: Systems, apparatuses, and methods for reducing chiplet interrupt latency are disclosed. A system includes one or more processing nodes, one or more memory devices, a communication fabric coupled to the processing unit(s) and memory device(s) via link interfaces, and a power management unit. The power management unit manages the power states of the various components and the link interfaces of the system. If the power management unit detects a request to wake up a given component, and the link interface to the given component is powered down, then the power management unit sends an out-of-band signal to wake up the given component in parallel with powering up the link interface. Also, when multiple link interfaces need to be powered up, the power management unit powers up the multiple link interfaces in an order which complies with voltage regulator load-step requirements while minimizing the latency of pending operations.

Abstract: Systems, apparatuses, and methods for dynamic buffer management in multi-client token flow control routers are disclosed. A system includes at least one or more processing units, a memory, and a communication fabric with a plurality of routers coupled to the processing unit(s) and the memory. A router servicing multiple active clients allocates a first number of tokens to each active client. The first number of tokens is less than a second number of tokens needed to saturate the bandwidth of each client to the router. The router also allocates a third number of tokens to a free pool, with tokens from the free pool being dynamically allocated to different clients. The third number of tokens is equal to the difference between the second number of tokens and the first number of tokens. An advantage of this approach is reducing the amount of buffer space needed at the router.

Abstract: Systems, apparatuses, and methods for processing multi-cast messages are disclosed. A system includes at least one or more processing units, one or more memory controllers, and a communication fabric coupled to the processing unit(s) and the memory controller(s). The communication fabric includes a plurality of crossbars which connect various agents within the system. When a multi-cast message is received by a crossbar, the crossbar extracts a message type indicator and a recipient type indicator from the message. The crossbar uses the message type indicator to determine which set of masks to lookup using the recipient type indicator. Then, the crossbar determines which one or more masks to extract from the selected set of masks based on values of the recipient type indicator. The crossbar combines the one or more masks with a multi-cast route to create a port vector for determining on which ports to forward the multi-cast message.

Abstract: Systems, apparatuses, and methods for routing interrupts on a coherency probe network are disclosed. A computing system includes a plurality of processing nodes, a coherency probe network, and one or more control units. The coherency probe network carries coherency probe messages between coherent agents. Interrupts that are detected by a control unit are converted into messages that are compatible with coherency probe messages and then routed to a target destination via the coherency probe network. Interrupts are generated with a first encoding while coherency probe messages have a second encoding. Cache subsystems determine whether a message received via the coherency probe network is an interrupt message or a coherency probe message based on an encoding embedded in the received message. Interrupt messages are routed to interrupt controller(s) while coherency probe messages are processed in accordance with a coherence probe action field embedded in the message.

Abstract: Systems, apparatuses, and methods for implementing priority adjustment forwarding are disclosed. A system includes at least one or more processing units, a memory, and a communication fabric coupled to the processing unit(s) and the memory. The communication fabric includes a plurality of arbitration points. When a client determines that its bandwidth requirements are not being met, the client generates and sends an in-band priority adjustment request to the nearest arbitration point. This arbitration point receives the in-band priority adjustment request and then identifies any pending requests which are buffered at the arbitration point which meet the criteria specified by the in-band priority adjustment request. The arbitration point adjusts the priority of any identified requests, and then the arbitration point forwards the in-band priority adjustment request on the fabric to the next upstream arbitration point which processes the in-band priority adjustment request in the same manner.