Importance

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Abstract

An apparatus and method for scheduling data transfers between a host and adapter. A schedule table data structure resides in a memory on the adapter. Each location in the schedule table represents a point in time at which data is to be transmitted from the adapter. A current time counter advances at the rate at which data is to be transmitted from the node. A pointer points to successive locations in the schedule table, and advances through the schedule table at a rate faster than the current time counter advances so that the value stored in the pointer represents a point in time which is ahead of the point in time currently represented by the value output from the current time counter. A request for a data transfer between the host and adapter is generated when a valid entry exists at the location pointed to by the pointer. The value of the pointer at the time the request is generated is stored as the last valid time. When a new entry is to be stored in the schedule table, it is stored at a location in the schedule table immediately after the location corresponding to the last valid time, and the pointer is reset to point to the location immediately after the location corresponding to the last valid time.

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First Claim