Abstract: An apparatus includes one or more interface circuits, an interconnect, a memory controller, a memory bridge, a packet DMA circuit, and a switch. The memory controller, the memory bridge, and the packet DMA circuit are coupled to the interconnect. Each interface circuit is coupled to a respective interface to receive packets and/or coherency commands from the interface. The switch is coupled to the interface circuits, the memory bridge, and the packet DMA circuit. The switch is configured to route the coherency commands from the interface circuits to the memory bridge and the packets from the interface circuits to the packet DMA circuit. The memory bridge is configured to initiate corresponding transactions on the interconnect in response to at least some of the coherency commands. The packet DMA circuit is configured to transmit write transactions on the interconnect to the memory controller to store the packets in memory.

Abstract: A node comprises at least one agent and an input/output (I/O) circuit coupled to an interconnect within the node. The I/O circuit is configured to communicate on a global interconnect to which one or more other nodes are coupled during use. Addresses transmitted on the interconnect are in a first local address space of the node, and addresses transmitted on the global interconnect are in a global address space. The first local address space includes at least a first region used to address at least a first resource of the node. The node is programmable, during use, to relocate the first region within the first local address space, whereby a same numerical value in the first local address space and a second local address space corresponding to one of the other nodes coupled to the global interconnect refers to the first resource in the node during use.

Abstract: A cache is configured to select a cache block for eviction in response to detecting a cache miss. The cache transmits the address of the cache block as a write transaction on an interface to the cache, and the cache captures the address from the interface and reads the cache block from the cache memory in response to the address. The read may occur similar to other reads in the cache, detecting a hit in the cache (in the cache storage location from which the cache block is being evicted). The write transaction is initiated before the corresponding data is available for transfer, and the use of the bus bandwidth to initiate the transaction provides an open access time into the cache for reading the evicted cache block.

Abstract: A system includes two or more agents and a distributed arbitration scheme for the bus to which the agents are connected. Thus, an arbiter corresponding to each agent is provided. The arbiters are reset using a first reset signal, while the agents are reset using a separate reset signal or signals. The arbiters are concurrently released from reset when the first reset signal is deasserted, and may have a consistent reset state to provide for synchronization of the arbiters. The agents may be independently released from reset by the separate reset signals. Accordingly, the arbiters may be synchronized and may remain synchronized even if the corresponding agents are released from reset at different times, or are temporarily held in reset for any reason.

Abstract: A cache may be programmed to disable one or more entries from allocation for storing memory data (e.g. in response to a memory transaction which misses the cache). Furthermore, the cache may be programmed to select which entries of the cache are disabled from allocation. Since the disabled entries are not allocated to store memory data, the data stored in the entries at the time the cache is programmed to disable the entries may remain in the cache. In one specific implementation, the cache also provides for direct access to entries in response to direct access transactions.

Abstract: A system may include two or more agents, at least some of which may cache data. In response to a read transaction, a caching agent may snoop its cached data and provide a response in a response phase of the transaction. Particularly, the response may include an exclusive indication used to represent both exclusive and modified states within that agent. In one embodiment, the agent responding exclusive may be responsible for providing the data for a read transaction, and may transmit an indication of which of the exclusive or modified state that agent had the data in concurrent with transmitting the data.

Abstract: A random number generator circuit includes a primary circuit configured to generate a value within a first range and a secondary circuit configured to generate a value within a second range. A detector circuit detects whether or not the value from the primary circuit is within the desired output range for the random number generator circuit, and selects either the value from the primary circuit or the value from the secondary circuit in response. The second range is the desired output range and the first range encompasses the second range. In one embodiment, the primary circuit has complex harmonics but may generate values outside the desired range. The secondary circuit may have less complex harmonics, but may generate values only within the desired range. In one implementation, the random number generator circuit is used to generate a replacement way for a cache.

Abstract: A system includes a bus and a circuit for precharging the bus. The circuit may be coupled to receive a clock signal associated with the bus, and may be configured to precharge a bus during an interval of the period of the clock signal, the interval being between a first edge (rising or falling) and the subsequent edge (falling or rising). A second interval within the period and excluding the interval may be used to perform a bus transfer. In this manner, both precharging and transfer may be performed in the same clock cycle. Bandwidth of the bus may be improved since transfers may occur each clock cycle, rather than having a non-transfer clock cycle for precharging.

Abstract: An apparatus includes one or more interface circuits, an interconnect, a memory controller, a memory bridge, a packet DMA circuit, and a switch. The memory controller, the memory bridge, and the packet DMA circuit are coupled to the interconnect. Each interface circuit is coupled to a respective interface to receive packets and/or coherency commands from the interface. The switch is coupled to the interface circuits, the memory bridge, and the packet DMA circuit. The switch is configured to route the coherency commands from the interface circuits to the memory bridge and the packets from the interface circuits to the packet DMA circuit. The memory bridge is configured to initiate corresponding transactions on the interconnect in response to at least some of the coherency commands. The packet DMA circuit is configured to transmit write transactions on the interconnect to the memory controller to store the packets in memory.

Abstract: A cache is configured to receive direct access transactions. Each direct access transaction explicitly specifies a way of the cache. The cache may alter the state of its replacement policy in response to a direct access transaction explicitly specifying a particular way of the cache. The state may be altered such that a succeeding cache miss causes an eviction of the particular way. Thus, a direct access transaction may be used to provide a deterministic setting to the replacement policy, providing predictability to the entry selected to store a subsequent cache miss. In one embodiment, the replacement policy may be a pseudo-random replacement policy. In one embodiment, a direct access transaction also explicitly specifies a cache storage entry to be accessed in response to the transaction.

Abstract: A cache is configured to select a cache block for eviction in response to detecting a cache miss. The cache transmits the address of the cache block as a write transaction on an interface to the cache, and the cache captures the address from the interface and reads the cache block from the cache memory in response to the address. The read may occur similar to other reads in the cache, detecting a hit in the cache (in the cache storage location from which the cache block is being evicted). The write transaction is initiated before the corresponding data is available for transfer, and the use of the bus bandwidth to initiate the transaction provides an open access time into the cache for reading the evicted cache block.

Abstract: A cache is configured to receive direct access transactions. Each direct access transaction explicitly specifies a cache storage entry to be accessed in response to the transaction. The cache may access the cache storage entry (bypassing the normal tag comparisons and hit determination used for memory transactions) and either read the data from the cache storage entry (for read transactions) or write data from the transaction to the cache storage entry (for write transactions). The direct access transactions may, for example, be used to perform testing of the cache memory. As another example, direct access transactions may be used to perform a reset of the cache (by writing known data to each cache entry). In embodiments employing error checking and correction (ECC) mechanisms, direct access write transactions could also be used to recover from uncorrectable ECC errors, by overwriting the failing data to eliminate the errant data.

Abstract: A system for servicing packet data transactions and input/output transactions includes an input port, an output port, a node controller, a packet manager, and a switching module. The input port is receives communications from a communicatively coupled processing device that include packet data transactions and input/output transactions. The output port transmits communications to a communicatively coupled processing device that include packet data transactions and input/output transactions. The node controller communicatively couples to a system bus of the processing device and services input/output transactions. The packet manager communicatively couples to the system bus of the processing device and services packet data transactions. A switching module communicatively couples to the input port, the output port, the node controller, and the packet manager and services the exchange of transaction cells among the input port, the output port, the node controller, and the packet manager.

Abstract: A system on a chip for network devices. In one implementation, the system on a chip may include (integrated onto a single integrated circuit), a processor and one or more I/O devices for networking applications. For example, the I/O devices may include one or more network interface circuits for coupling to a network interface. In one embodiment, coherency may be enforced within the boundaries of the system on a chip but not enforced outside of the boundaries.

Abstract: A cache is configured to receive direct access transactions. Each direct access transaction explicitly specifies a way of the cache. The cache may alter the state of its replacement policy in response to a direct access transaction explicitly specifying a particular way of the cache. The state may be altered such that a succeeding cache miss causes an eviction of the particular way. Thus, a direct access transaction may be used to provide a deterministic setting to the replacement policy, providing predictability to the entry selected to store a subsequent cache miss. In one embodiment, the replacement policy may be a pseudo-random replacement policy. In one embodiment, a direct access transaction also explicitly specifies a cache storage entry to be accessed in response to the transaction.

Abstract: A random number generator circuit includes a primary circuit configured to generate a value within a first range and a secondary circuit configured to generate a value within a second range. A detector circuit detects whether or not the value from the primary circuit is within the desired output range for the random number generator circuit, and selects either the value from the primary circuit or the value from the secondary circuit in response. The second range is the desired output range and the first range encompasses the second range. In one embodiment, the primary circuit has complex harmonics but may generate values outside the desired range. The secondary circuit may have less complex harmonics, but may generate values only within the desired range. In one implementation, the random number generator circuit is used to generate a replacement way for a cache.

Abstract: An apparatus includes one or more interface circuits, an interconnect, a memory controller, a memory bridge, a packet DMA circuit, and a switch. The memory controller, the memory bridge, and the packet DMA circuit are coupled to the interconnect. Each interface circuit is coupled to a respective interface to receive packets and/or coherency commands from the interface. The switch is coupled to the interface circuits, the memory bridge, and the packet DMA circuit. The switch is configured to route the coherency commands from the interface circuits to the memory bridge and the packets from the interface circuits to the packet DMA circuit. The memory bridge is configured to initiate corresponding transactions on the interconnect in response to at least some of the coherency commands. The packet DMA circuit is configured to transmit write transactions on the interconnect to the memory controller to store the packets in memory.

Abstract: A system may include two or more agents, at least some of which may cache data. In response to a read transaction, a caching agent may snoop its cached data and provide a response in a response phase of the transaction. Particularly, the response may include an exclusive indication used to represent both exclusive and modified states within that agent. In one embodiment, the agent responding exclusive may be responsible for providing the data for a read transaction, and may transmit an indication of which of the exclusive or modified state that agent had the data in concurrent with transmitting the data.

Abstract: An agent may be coupled to receive a clock signal associated with the bus, and may be configured to drive a signal responsive to a first edge (rising or falling) of the clock signal and to sample signals responsive to the second edge. The sampled signals may be evaluated to allow for the driving of a signal on the next occurring first edge of the clock signal. By using the first edge to drive signals and the second edge to sample signals, the amount of time dedicated for signal propagation may be one half clock cycle. Bandwidth and/or latency may be positively influenced. In some embodiments, protocols which may require multiple clock cycles on other buses may be completed in fewer clock cycles. For example, certain protocols which may require two clock cycles may be completed in one clock cycle. In one specific implementation, for example, arbitration may be completed in one clock cycle. Request signals may be driven responsive to the first edge of the clock signal and sampled responsive to the second edge.

Abstract: A cache is configured to receive direct access transactions. Each direct access transaction explicitly specifies a cache storage entry to be accessed in response to the transaction. The cache may access the cache storage entry (bypassing the normal tag comparisons and hit determination used for memory transactions) and either read the data from the cache storage entry (for read transactions) or write data from the transaction to the cache storage entry (for write transactions). The direct access transactions may, for example, be used to perform testing of the cache memory. As another example, direct access transactions may be used to perform a reset of the cache (by writing known data to each cache entry). In embodiments employing error checking and correction (ECC) mechanisms, direct access write transactions could also be used to recover from uncorrectable ECC errors, by overwriting the failing data to eliminate the errant data.