Processor Bypass Detection Using Wakeup CAM to Reduce PRF Power
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Solution Overview
Problem
Conventional processor designs face bottlenecks in scheduling and power consumption due to delays in mapping and queuing processes, particularly in multi-pipeline execution units, which affect processing speed and efficiency.
Innovation Solution
A method is introduced to reduce power consumption by disabling physical register file (PRF) read operations using a wakeup content-addressable memory (CAM) that compares destination physical register tags with source tags, enabling the bypassing of PRF reads when a match is found, thereby reducing unnecessary power usage and enhancing processing speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional processor designs use multi-pipeline execution units with dedicated queues, then processing speed is improved, but power consumption increases due to unnecessary PRF read operations
Solution Approach 1:
The bypass detection logic performs preliminary comparison of source and destination register tags before PRF read operations are executed. By detecting potential bypass opportunities in advance and generating control signals to disable unnecessary PRF reads, the system eliminates wasteful power consumption while maintaining the high processing speed enabled by multi-pipeline execution units
2Productivity
If dedicated queues are used for multiple EX pipelines, then execution throughput is improved, but scheduling complexity and bottlenecks increase
Solution Approach 1:
The patent merges the queue structures across multiple EX pipelines into a unified queue system. This consolidation reduces the number of separate queue management operations needed, simplifying the scheduling logic while maintaining high execution throughput. The unified approach eliminates bottlenecks associated with managing multiple dedicated queues
3Reliability
If PRF read operations are always performed, then data availability is ensured, but power consumption increases due to unnecessary reads
Solution Approach 1:
The bypass detection logic implements a feedback mechanism that monitors source and destination register tags, compares them, and generates control signals based on the comparison results. When a match is detected, the feedback signal disables the corresponding PRF read operation, ensuring data availability is maintained through the bypass path while eliminating unnecessary power consumption from redundant reads
Data Source
AI summary
A method and apparatus are described for reducing power consumption in a processor. A micro-operation is selected for execution, and a destination physical register tag of the selected micro-operation is compared to a plurality of source physical register tags of micro-operations dependent upon the selected micro-operation. If there is a match between the destination physical register tag and one of the source physical register tags, a corresponding physical register file (PRF) read operation is disabled. The comparison may be performed by a wakeup content-addressable memory (CAM) of a scheduler. The wakeup CAM may send a read control signal to the PRF to disable the read operation. Disabling the corresponding PRF read operation may include shutting off power in the PRF and related logic.