Apple Inc.
Non-shifting reservation station

Abstract:

Systems, apparatuses, and methods for implementing a non-shifting reservation station. A dispatch unit may write an operation into any entry of a reservation station. The reservation station may include an age matrix for determining the relative ages of the operations stored in the entries of the reservation station. The reservation station may include selection logic which is configured to pick the oldest ready operation from the reservation station based on the values stored in the age matrix. The selection logic may utilize control logic to mask off columns of an age matrix corresponding to non-ready operation so as to determine which operation is the oldest ready operation in the reservation station. Also, the reservation station may be configured to dequeue operations early when these operations do not have load dependency.