Speculative Clock Gating for Digital Logic Circuits
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Solution Overview
Problem
Traditional precise clock gating in digital logic circuits incurs significant delays, making it infeasible in certain pipeline designs due to communication and logic delays, which can result in power consumption issues and performance limitations.
Innovation Solution
Implementing speculative clock gating by generating a valid control signal and a speculative valid control signal using a subset of control inputs, allowing the clock signal to be sent directly to some registers while gating others, reducing delay and enabling clock gating where precise gating would be impractical.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If precise clock gating is implemented using all control inputs, then power savings are maximized, but signal delay increases making gating infeasible
Solution Approach 1:
The patent applies partial action by using a subset of control inputs to generate the speculative clock gating signal rather than all control inputs. This reduces the logic complexity and signal delay while accepting that some power savings opportunities may be missed, thus resolving the contradiction between maximizing power savings and minimizing signal delay
Solution Approach 2:
The speculative clock gating signal is generated in advance using only essential control inputs, allowing the clock gating decision to be made earlier in the pipeline. This preliminary action reduces the critical path delay while still achieving significant power savings, addressing the feasibility issue of precise clock gating
2Measurement precision
If precise clock gating signals are generated using all control inputs, then clock gating accuracy is maximized, but circuit complexity increases
Solution Approach 1:
The patent uses only a subset of control inputs to generate the speculative clock gating signal, reducing the logic circuit complexity while maintaining sufficient gating accuracy for power savings. This partial action approach balances accuracy requirements with circuit complexity constraints
Solution Approach 2:
The control inputs are segmented into two groups: those used for speculative clock gating signal generation and those not used. This segmentation simplifies the clock gating logic by identifying and utilizing only the essential control inputs, thereby reducing circuit complexity while preserving key functionality
3Loss of energy
If clock gating is implemented without speculative approach, then power savings are achieved, but signal delay makes gating infeasible in deep pipelines
Solution Approach 1:
The speculative clock gating signal is generated preliminarily using a reduced set of control inputs, enabling clock gating decisions to be made earlier in the pipeline. This preliminary generation reduces signal delay and makes clock gating feasible in deep pipeline designs where traditional precise gating would be too slow
Solution Approach 2:
By using only a subset of control inputs for speculative gating, the patent reduces logic delay while maintaining sufficient power savings. This partial action enables clock gating to be implemented in pipeline stages where full precise gating would exceed timing constraints, thus improving gating feasibility
Data Source
AI summary
A method for implementing speculative clock gating of digital logic circuits in a multiple stage pipeline design includes generating, in a first pipeline stage n, a valid control signal that is input to a first register in a second pipeline stage n+1, the valid control signal indicative of when an operation is qualified to be performed by the second pipeline stage n+1; and generating, in the first pipeline stage, a speculative valid control signal that is used to gate a clock signal to a plurality of additional registers in the second pipeline stage, wherein the speculative valid control signal is generated using only a subset of a total number of control inputs used in generating the valid control signal, and wherein the clock signal is sent directly, without gating, to the first register in the second pipeline stage.