Clock-Gating Multicycle Instructions via Precise Enable Computation
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Solution Overview
Problem
Current clock-gating techniques are inefficient for multicycle instructions, leading to unnecessary power consumption and heating due to imprecise detection and late activation of logic blocks, which hampers thermal design power management and processor performance.
Innovation Solution
A method and system for precise clock-gating of multicycle instructions, involving the computation of enable values after initial cycles to disable unnecessary logic blocks, using control latches and OR gates to manage clock domains and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant clocking of logic blocks is used to ensure instruction execution, then reliability of instruction processing is improved, but power consumption and heat dissipation increase significantly
Solution Approach 1:
The patent implements dynamic clock gating control where the clock signal to logic blocks is dynamically adjusted based on the actual execution state of multicycle instructions. The system transitions from static constant clocking to dynamic clocking that adapts to the specific needs of each instruction, enabling clock signals to be gated off when not needed and restored when required, thus reducing power consumption while maintaining reliability.
Solution Approach 2:
The patent employs feedback mechanisms through detection circuits that monitor the execution state of instructions and provide signals to control the clock gating logic. The system detects whether multicycle instructions are currently being executed and uses this feedback information to dynamically control the clock signals, ensuring that logic blocks receive clock signals only when necessary for instruction execution, thereby balancing reliability and power consumption.
2Use of energy by moving object
If precise detection of multicycle instruction execution state is implemented, then power consumption is reduced through accurate clock gating, but device complexity increases
Solution Approach 1:
The patent segments the detection and control functionality into distinct modular components: detection circuits that monitor instruction execution state, control logic that processes detection signals, and clock gating units that execute the control decisions. This segmentation allows each component to be optimized independently and simplifies the overall design by distributing complexity across multiple specialized modules rather than requiring a single complex detection system.
Solution Approach 2:
The patent introduces intermediary control logic and signaling mechanisms that bridge the detection circuits and clock gating units. These intermediaries process the raw detection signals and translate them into appropriate clock control signals, simplifying the interface between detection and execution components while enabling precise control without requiring direct complex coupling between all elements.
3Device complexity
If late detection of multicycle instructions is used, then device complexity is reduced, but unnecessary logic blocks remain enabled causing increased power consumption
Solution Approach 1:
The patent implements preliminary detection mechanisms that identify multicycle instructions early in the execution pipeline, before the instruction fully completes. The detection circuits are positioned to capture the execution state at early stages, allowing the clock gating control to be activated in advance. This preliminary action enables the system to gate off clock signals to unnecessary logic blocks earlier than late detection would allow, preventing energy waste while maintaining manageable device complexity.
Data Source
AI summary
A system and a method of clock-gating for multicycle instructions are provided. For example, the method includes enabling a plurality of logic blocks that include a subset of multicycle (MC) logic blocks and a subset of pipeline logic blocks. The method also includes computing a precise enable computation value after a plurality of cycles of executing an instruction, and disabling one or more of the subset of multicycle (MC) logic blocks based on the precise enable computation value. Also, at least the subset of pipeline logic blocks needed to compute the instruction remains on.