Intel Corporation

Pierre Michaud

Stephan Jourdan

Per H Hammarlund

Douglas M Carmean

Mark C Davis

Alexandre J Farcy

Morris Marden

Robert L Hinton

Chris Yunker

Systems and methods of managing threads provide for supporting a plurality of logical threads with a plurality of simultaneous physical threads in which the number of logical threads may be greater than or less than the number of physical threads. In one approach, each of the plurality of logical threads is maintained in one of a wait state, an active state, a drain state, and a stall state. A state machine and hardware sequencer can be used to transition the logical threads between states based on triggering events and whether or not an interruptible point has been encountered in the logical threads. The logical threads are scheduled on the physical threads to meet, for example, priority, performance or fairness goals. It is also possible to specify the resources that are available to each logical thread in order to meet these and other, goals. In one example, a single logical thread can speculatively use more than one physical thread, pending a selection of which physical thread should be committed.

Decoupling the number of logical threads from the number of simultaneous physical threads in a processor

Systems and methods of processing addresses provide for receiving a full linear address of an instruction and reducing a size of the full linear address to obtain a reduced linear address. A data block can be retrieved from a data array if the reduced linear address corresponds to a tag in a tag array, where the tag array is associated with the data array. The reduced linear address enables the tag array to either be smaller in size or achieve enhanced performance. The data array may be a prediction array of a branch predictor or a cache array of a cache.

Retrieving data blocks with reduced linear addresses

Systems and methods of processing branch instructions provide for a bimodal predictor and a plurality of global predictors. The bimodal predictor is coupled to a prediction selector, where the bimodal predictor generates a bimodal prediction for branch instructions. The plurality of global predictors is coupled to the prediction selector, where each global predictor generates a corresponding global prediction for a branch instruction using different history or stew lengths. The prediction selector selects branch predictions from the bimodal prediction and the global predictions in order to arbitrate between predictors. The arbitration, update, and allocation schemes are designed to choose the most accurate predictor for each branch. Lower level predictors are used as filters to increase effective predictor capacity. Allocate and update schemes minimize aliasing between predictors. Branch predictors incorporating a plurality of global predictors in this fashion are more adaptive than conventional predictors with fixed branch history lengths and are able to achieve superior accuracy.

Predicting instruction branches with a plurality of global predictors using varying amounts of history instruction

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Bruz, France

Pierre Michaud