Importance

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Abstract

A hardware-based linked list queues memory transactions in a memory controller. The memory controller includes a plurality of memory controller agents. Each agent has a head flag, a tail flag, and a next agent field, thereby allowing the agents to be arranged into linked lists. Memory transactions are received from cacheable entities of a computer system at an incoming memory transaction dispatch unit via an interconnection fabric. The incoming transactions are then presented to the plurality of agents. For each incoming read transaction, one of the agents will accept the transaction. If there are pending memory read transactions for the memory line, then the accepting agent joins a linked list of agents that are queued up to access that memory line. The accepting agent drives its index out onto a bus that connects all agents. One agent in the linked list will have its tail flag set, and that agent will clear its tail flag and latch into its next agent field the index provided by the accepting agent. Also, the accepting agent will set its tail flag to indicate that it is now at the end of the linked list. When the head agent finishes a transaction, the head agent advances the list by notifying the next agent that it is now the new head agent. The old head agent then clears a valid flag, indicating that it can now accept a new transaction, and the new head agent sets its head flag.

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First Claim