Pipelined Processor Bypass Circuit Reduces Register File Power
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Solution Overview
Problem
Data dependency in instruction processors leads to reduced throughput due to the need for operands to be stored in register files before they can be used, resulting in inefficiencies and increased power consumption as register files grow larger.
Innovation Solution
Implementing a bypass mechanism that allows results to be stored in bypass registers instead of the main register file when they will only be used via a bypass path, reducing the need for writing to the register file and thereby lowering power consumption, using a bypass control unit to manage the bypassing of results based on operand and result address matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the register file size is increased to speed up execution, then execution speed is improved, but power consumption increases
Solution Approach 1:
The patent segments the register file into two distinct parts: a full register file for general use and a smaller bypass register file for temporary results. This segmentation allows the system to maintain a large register file capacity while using a smaller, lower-power subset for frequent operations, thereby reducing overall power consumption while preserving execution speed.
Solution Approach 2:
The patent applies local quality by providing different characteristics to different parts of the register file system. The bypass register file is optimized for speed and immediate access, while the main register file provides full storage capacity. This localized optimization allows critical paths to operate at high speed without requiring the entire system to consume maximum power.
2Use of energy by moving object
If a bypass mechanism is implemented to store results in bypass registers instead of the main register file, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent merges the bypass register file with the main register file system, allowing both to coexist and operate together. The bypass file handles temporary results while the main file handles persistent storage, and they are integrated through shared control logic and address routing, reducing the need for completely separate systems.
Solution Approach 2:
The bypass register file serves multiple functions: it acts as a temporary storage for results that will be immediately reused, as a buffer for pipeline operations, and as a power-saving mechanism. This multi-functionality justifies the added complexity by providing several benefits from a single structural addition.
3Reliability
If results are always written to the register file, then data availability is ensured, but power consumption increases
Solution Approach 1:
The patent implements preliminary action by determining at compile time which results will be immediately reused and should be stored in the bypass register file. This advance planning ensures that data availability is maintained for critical operations while avoiding unnecessary writes to the main register file, thereby reducing power consumption.
Solution Approach 2:
The system uses feedback from the compiler analysis to control the bypass mechanism. The compiler identifies data dependencies and reuse patterns, providing feedback about which results should be bypassed. This feedback-driven approach ensures data availability is maintained exactly where needed without wasting power on redundant storage operations.
Data Source
AI summary
An instruction processing device has a of pipe-line stage with a functional unit for executing a command from an instruction. A first register unit is coupled to the functional unit for storing a result of execution of the command when the command has reached a first one of the pipeline stages, and for supplying bypass operand data to the functional unit. A register file is coupled to the functional unit for storing the result when the command has reached a second one of the pipeline stages, downstream from the first one of the pipeline stages, and for supplying operand data to the functional unit. A disable circuit is coupled to selectively disable storing of the results in the register file under control of the instructions.