Abstract:
A processor may include an instruction distribution circuit and a plurality of execution pipelines. The instruction distribution circuit may distribute a conditional instruction to a first execution pipeline for execution when the conditional instruction is associated with a prediction of a high confidence level, or to a second execution pipeline for execution when the conditional instruction is associated with a prediction of a low confidence level. The second execution pipeline, not the first execution pipeline, may directly instruct the processor to obtain an instruction from a target address for execution, when the conditional instruction is mispredicted. Thus, when the conditional instruction is distributed to the first execution pipeline for execution and determined to be mispredicted, the first execution pipeline may cause the conditional instruction to be re-executed in the second execution pipeline to cause the instruction from the correct target address to be obtained for execution.
Abstract:
A processor may include a physical register file and a register renamer. The register renamer may be organized into even and odd banks of entries, where each entry stores an identifier of a physical register. The register renamer may be indexed by a register number of an architected register, such that the renamer maps a particular architected register to a corresponding physical register. Individual entries of the renamer may correspond to architected register aliases of a given size. Renaming aliases that are larger than the given size may involve accessing multiple entries of the renamer, while renaming aliases that are smaller than the given size may involve accessing a single renamer entry.
Abstract:
In an embodiment, a system may include multiple processors and an automatic power state controller (APSC) configured to switch the processors between various operating points. The operating points may be described by data programmed into the APSC, and the APSC may include a register that is programmable with a target operating point request identifying a target operating point for the processors from among the described operating points. The data describing the operating points may also include an indication of whether or not the number of processors that may be concurrently active at the operating point is limited. Based on the indication and the number of active processors, the APSC may override the requested operating point with a reduced operating point. In some embodiments, a digital power estimator (DPE) may monitor operation of the processors and may throttle the processors when high power consumption is detected.
Abstract:
An apparatus for performing instruction throttling for a multi-processor system is disclosed. The apparatus may include a power estimation circuit, a table, a comparator, and a finite state machine. The power estimation circuit may be configured to receive information on high power instructions issued to a first processor and a second processor, and generate a power estimate dependent upon the received information. The table may be configured to store one or more pre-determined power threshold values, and the comparator may be configured to compare the power estimate with at least one of the pre-determined power threshold values. The finite state machine may be configured to adjust the throttle level of the first and second processors dependent upon the result of the comparison.
Abstract:
Various techniques for processing and pre-decoding branches within an IT instruction block. Instructions are fetched and cached in an instruction cache, and pre-decode bits are generated to indicate the presence of an IT instruction and the likely boundaries of the IT instruction block. If an unconditional branch is detected within the likely boundaries of an IT instruction block, the unconditional branch is treated as if it were a conditional branch. The unconditional branch is sent to the branch direction predictor and the predictor generates a branch direction prediction for the unconditional branch.
Abstract:
A circuit for implementing a branch target buffer. The branch target buffer may include a memory that stores a plurality of entries. Each entry may include a tag value, a target value, and a prediction accuracy value. A received index value corresponding to an indirect branch instruction may be used to select one of entries of the plurality of entries, and a received tag value may then be compared to the tag value of the selected entries in the memory. An entry in the memory may be selected in response to a determination that the received tag does not match the tag value of compared entries. The selected entry may be allocated to the indirect instruction branch dependent upon the prediction accuracy values of the plurality of entries.
Abstract:
A system and method for efficiently reducing the latency of load operations. In various embodiments, logic of a processor accesses a prediction table after fetching instructions. For a prediction table hit, the logic executes a load instruction with a retrieved predicted address from the prediction table. For a prediction table miss, when the logic determines the address of the load instruction and hits in a learning table, the logic updates a level of confidence indication to indicate a higher level of confidence when a stored address matches the determined address. When the logic determines the level of confidence indication stored in a given table entry of the learning table meets a threshold, the logic allocates, in the prediction table, information stored in the given entry. Therefore, the predicted address is available during the next lookup of the prediction table.
Abstract:
In an embodiment, a system may include multiple processors and an automatic power state controller (APSC) configured to switch the processors between various operating points. The operating points may be described by data programmed into the APSC, and the APSC may include a register that is programmable with a target operating point request identifying a target operating point for the processors from among the described operating points. The data describing the operating points may also include an indication of whether or not the number of processors that may be concurrently active at the operating point is limited. Based on the indication and the number of active processors, the APSC may override the requested operating point with a reduced operating point. In some embodiments, a digital power estimator (DPE) may monitor operation of the processors and may throttle the processors when high power consumption is detected.
Abstract:
A system and method for efficiently reducing the latency of load operations. In various embodiments, logic of a processor accesses a prediction table after fetching instructions. For a prediction table hit, the logic executes a load instruction with a retrieved predicted address from the prediction table. For a prediction table miss, when the logic determines the address of the load instruction and hits in a learning table, the logic updates a level of confidence indication to indicate a higher level of confidence when a stored address matches the determined address. When the logic determines the level of confidence indication stored in a given table entry of the learning table meets a threshold, the logic allocates, in the prediction table, information stored in the given entry. Therefore, the predicted address is available during the next lookup of the prediction table.
Abstract:
A system for managing a change in a frequency of a clock signal, including a clock generator configured to output the clock signal, a clock divider coupled to the output of the clock generator, a processor configured to select the frequency of the clock signal, and a clock management circuit. The clock management circuit may be configured to set the clock generator to adjust the clock signal to the selected frequency. The clock management circuit may be further configured to adjust a divisor value of the clock divider in a plurality of steps in response to a determination the clock signal stabilized at the selected frequency. A new divisor value may be selected during each step in the plurality of steps and each step may occur after a given time period.