摘要:
An information handling system includes a processor that throttles the instruction fetcher whenever the inaccuracy, or lack of confidence, in branch predictions for branch instructions stored in a branch instruction queue exceeds a predetermined threshold confidence level of inaccuracy or error. In this manner, fetch operations slow down to conserve processor power when it is likely that the processor will mispredict the outcome of branch instructions. Fetch operations return to full speed when it is likely that the processor will correctly predict the outcome of branch instructions.
摘要:
A system and method for a high frequency stall design is presented. An issue unit includes a first instruction stage, a second instruction stage, and issue control logic. During a first instruction cycle, the issue unit performs two tasks, which are 1) the instructions located in the first instruction stage are moved to a second instruction stage, and 2) the issue control logic determines whether to issue or stall the instructions that are moved to the second instruction stage based upon their particular instruction attributes and the issue control unit's previous state. During a second instruction cycle that immediately follows the first instruction cycle, the second instruction stage's instructions are either issued or stalled based upon the issue control logic's decision from the first instruction cycle.
摘要:
A compressor circuit suitable for use in an arithmetic unit of a microprocessor includes a first stage, a second stage, a carry circuit, and a sum circuit. The first stage is configured to receive a set of four input signals. The first stage generates a first intermediate signal indicative of the XNOR of a first pair of the input signals and a second intermediate signal indicative of the XNOR of a second pair of the input signals. The second stage configured to receive at least a portion of the signals generated by the first stage. The second stage generates first and second control signals where the first control signal is indicative of the XNOR of the four input signals and the second control signal is the logical complement of the first signal. The carry circuit is configured to receive at least one of the control signals and further configured to generate a carry bit based at least in part on the state of the received control signal. The sum circuit is configured to receive at least one of the control signals and further configured to generate a sum bit based at least in part on the state of the received control signal. At least one of the first stage, second stage, sum circuit, and carry circuit include at least one CMOS transmission gate comprised of an n-channel transistor and a p-channel transistor having their source/drain terminals connected in parallel, wherein the p-channel transistor gate is driven by the logical complement of the n-channel transistor gate. In one embodiment, the first stage, second stage, carry circuit, and sum circuit are comprised primarily of such transmission gates to the exclusion of conventional CMOS complementary passgate logic.
摘要:
A computer-based method automatically synthesizes, optimizes and compiles high performance control logic using SRCMOS LOGIC ARRAY MACROS, abbreviated as SLAMs. The method includes a series of steps that transform a high level design description into a set of SLAMs, and includes the steps of partitioning the logic description of a unit into blocks that are suitable for mapping to a target SLAM structure; mapping each logic partition to the target SLAM structure; creating a configuration and relative layout for the internal structure for each SLAM; creating an external description for each SLAM, each description being of sufficient detail to carry out physical design and integration of the unit which contains the SLAM; assembling the partitions implemented as SLAMs with other macros in the unit; resolving interface conflicts between the different macros by selecting appropriate signal interfaces for various SLAMs; repeatedly changing the external specifications of the various SLAMs; analyzing the performance of the unit; automatically compiling the schematic and layout of each SLAM within the unit based on the configuration and relative layout; and assembling the macros and analyzing the design for design rule violations.
摘要:
Tracking the order of issued instructions using a counter is presented. In one embodiment, a saturating, decrementing counter is used. The counter is initialized to a value that corresponds to the processor's commit point. Instructions are issued from a first issue queue to one or more execution units and one or more second issue queues. After being issued by the first issue queue, the counter associated with each instruction is decremented during each instruction cycle until the instruction is executed by one of the execution units. Once the counter reaches zero it will be completed by the execution unit. If a flush condition occurs, instructions with counters equal to zero are maintained (i.e., not flushed or invalidated), while other instructions in the pipeline are invalidated based upon their counter values.
摘要:
A method of obtaining data, comprising at least one sector, for use by at least a first thread wherein each processor cycle is allocated to at least one thread, includes the steps of: requesting data for at least a first thread; upon receipt of at least a first sector of the data, determining whether the at least first sector is aligned with the at least first thread, wherein a given sector is aligned with a given thread when a processor cycle in which the given sector will be written is allocated to the given thread; responsive to a determination that the at least first sector is aligned with the at least first thread, bypassing the at least first sector, wherein bypassing a sector comprises reading the sector while it is being written; and responsive to a determination that the at least first sector is not aligned with the at least first thread, delaying the writing of the at least first sector until the occurrence of a processor cycle allocated to the at least first thread by retaining the at least first sector in at least one alignment register, thereby permitting the at least first sector to be bypassed.
摘要:
Tracking the order of issued instructions using a counter is presented. In one embodiment, a saturating, decrementing counter is used. The counter is initialized to a value that corresponds to the processor's commit point. Instructions are issued from a first issue queue to one or more execution units and one or more second issue queues. After being issued by the first issue queue, the counter associated with each instruction is decremented during each instruction cycle until the instruction is executed by one of the execution units. Once the counter reaches zero it will be completed by the execution unit. If a flush condition occurs, instructions with counters equal to zero are maintained (i.e., not flushed or invalidated), while other instructions in the pipeline are invalidated based upon their counter values.
摘要:
An information handling system includes a processor that throttles an instruction fetcher whenever a group of instructions in a branch instruction queue together exhibits a confidence in the accuracy of branch predictions of branch instructions therein that is less than a first predetermined threshold confidence threshold. In one embodiment, the processor includes a fetch throttle controller that inhibits fetch throttling by the instruction fetcher when confidence in the accuracy of a branch prediction for a particular currently issued branch instruction exhibits less than a second predetermined threshold confidence threshold.
摘要:
Dynamic power management in a processor design is presented. A pipeline stage's stall detection logic detects a stall condition, and sends a signal to idle detection logic to gate off the pipeline's register clocks. The stall detection logic also monitors a downstream pipeline stage's stall condition, and instructs the idle detection logic to gate off the pipeline stage's registers when the downstream pipeline stage is in a stall condition as well. In addition, when the pipeline stage's stall detection logic detects a stall condition, either from the downstream pipeline stage or from its own pipeline units, the pipeline stage's stall detection logic informs an upstream pipeline stage to gate off its clocks and thus, conserve more power.
摘要:
An information handling system employs a processor that includes a thread priority controller. The processor includes a memory array that stores instruction threads including branch instructions. A branch unit in the processor sends flush information to the thread priority controller when a particular branch instruction in a particular instruction thread requires a flush operation. The flush information may indicate the correctness of incorrectness of a branch prediction for the particular branch instruction and thus the necessity of a flush operation. The flush information may also include a thread ID of the particular thread. If the flush information for the particular branch instruction of the particular thread indicates that a flush operation is necessary, the thread priority controller in response speculatively increases or boosts the priority of the particular instruction thread including the particular branch instruction. In this manner, a fetcher in the processor obtains ready access to the particular thread in the memory array.