Apple Inc.

Vinodh R Cuppu

Nachiappan Chidambaram Nachiappan

Jaideep Dastidar

Shawn Munetoshi Fukami

Yiu Chun Tse

Deniz Balkan

Benjamin K Dodge

Hengsheng Geng

Matthew R Johnson

David L Trawick

Ripudaman Singh

Systems, apparatuses, and methods for controlling bandwidth through shared transaction limits are described. An apparatus includes at least a plurality of agents, a plurality of transaction-limit (T-Limit) nodes, a T-Limit manager, and one or more endpoints. The T-Limit manager creates a plurality of credits for the plurality of agents to send transactions to a given endpoint. Then, the T-Limit manager partitions the credits into N+1 portions for N agents, wherein the extra N+1 portion is a shared pool for use by agents when they run out of their private credits. The T-Limit manager assigns a separate private portion of the N portions to the N agents for use by only the corresponding agent. When an agent runs out of private credits, the agent's T-Limit node sends a request to the T-Limit manager for credits from the shared pool.

Systems and methods to control bandwidth through shared transaction limits

A system and method for efficiently arbitrating traffic on a bus. A computing system includes a fabric for routing traffic among one or more agents and one or more endpoints. The fabric includes multiple arbiters in an arbitration hierarchy. Arbiters store traffic in buffers with each buffer associated with a particular traffic type and a source of the traffic. Arbiters maintain a respective urgency counter for keeping track of a period of time traffic of a particular type is blocked by upstream arbiters. When the block is removed, the traffic of the particular type has priority for selection based on the urgency counter. When arbiters receive feedback from downstream arbiters or sources, the arbiters adjust selection priority accordingly. For example, changes in bandwidth requirement, low latency tolerance and active status cause adjustments in selection priority of stored requests.

Systems and methods for arbitrating traffic in a bus

Systems, apparatuses, and methods for implementing a configurable packet arbiter with minimum progress guarantees are described. An arbiter includes at least control logic, a plurality of counters, and a tunables matrix. The tunables matrix stores values for a plurality of configurable parameters for the various transaction sources of the arbiter. These parameter values determine the settings that the arbiter uses for performing arbitration. One of the parameters is a minimum progress guarantee value that specifies how many times each source should be picked per interval. The minimum progress guarantee helps to reduce arbitration-related jitter. Also, the arbiter includes a grant counter for each source. After the minimum progress guarantees are satisfied, the arbiter selects the source with the lowest grant counter among the sources with packets eligible for arbitration. Then, the arbiter increments the grant counter of the winning source by a grant increment amount specific to the source.

Configurable packet arbitration with minimum progress guarantees

A system and method for efficiently allocating data storage to agents. A computing system includes an interconnect with intermediate buffers for storing transactions and corresponding payload data during transport between sources and destinations. A data storage limit is set on an amount of data storage corresponding to outstanding transactions for each of the multiple sources based on the initial buffer assignments. A number of outstanding transactions for each of the multiple sources is limited based on a corresponding data storage limit. If the rate of allocation of a given buffer assigned to a first source exceeds a threshold, then a second source is selected with available space exceeding a threshold in an assigned buffer. If it is determined the second source is not assigned to a buffer with a rate of allocation exceeding a threshold, then buffer storage is reassigned from the second source to the first source.

Systems and methods for providing a back pressure free interconnect

A system and method for efficiently routing data in a communication fabric. A computing system includes a fabric for routing data among one or more agents and a memory controller for system memory. The fabric includes multiple hierarchical clusters with a split topology where the data links are physically separated from the control links. A given cluster receives a write command and associated write data, and stores them in respective buffers. The given cluster marks the write command as a candidate to be issued to the memory controller when it is determined the write data will arrive ahead of the write command at the memory controller after being issued. The given cluster prevents the write command from becoming a candidate to be issued when it is determined the write data may not arrive ahead of the write command at the memory controller.

Systems and methods for controlling data on a bus using latency

A system and method for efficiently bridging two communication protocols. In various embodiments, a computing system includes an interconnect for routing traffic among agents and endpoints. The agents use a first communication protocol and the endpoints use a second communication protocol that differs from the first protocol with regard to at least the ordering that is enforced between transactions. A bridge selects transactions of a first type and a second type used in the first protocol for processing based on the first protocol ordering while using acknowledgments used by the second protocol.

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San Jose, CA, United States of America

Vinodh R Cuppu