Vector Mask Clock Gating for Processor Power Efficiency
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Solution Overview
Problem
Advanced vector extensions (AVX) processors experience power inefficiency due to processing operations that are discarded because of zeroed mask bits, leading to unnecessary power consumption in vector arithmetic logic units (ALUs).
Innovation Solution
Implementing clock gating within the vector ALU pipeline to shut down or reduce power consumption of processing elements based on mask values, specifically at the data element level, during vector instruction execution, including stages like vector register read, data bus dispatch, shuffle, ALU execution, and write-back.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If vector ALU processes all data elements in parallel regardless of mask values, then processing speed is maintained, but power consumption increases due to unnecessary operations on inactive elements
Solution Approach 1:
The vector ALU is segmented into multiple independent data element processing units, each capable of being individually enabled or disabled through clock gating. This segmentation allows the processor to activate only the specific processing elements needed for the current instruction, rather than running all elements in parallel, thereby reducing power consumption while maintaining processing speed for active elements.
Solution Approach 2:
The patent implements dynamic clock gating control that adjusts the operational state of vector ALU elements based on real-time mask values. The clock signal to each processing element is dynamically enabled or disabled according to the corresponding mask bit, allowing the system to adapt its power consumption profile to the actual computational needs without sacrificing processing throughput for active elements.
2Use of energy by moving object
If clock gating is implemented at the data element level based on mask values, then power efficiency is improved, but device complexity increases
Solution Approach 1:
The patent merges the mask value extraction logic with the existing instruction decoding and execution pipeline. The mask values are extracted and distributed to clock gating control units that are integrated into the vector ALU structure, rather than adding completely separate control mechanisms. This merging approach enables fine-grained power management at the data element level while minimizing the increase in device complexity through shared infrastructure.
3Productivity
If all vector ALU operations are executed, then processing throughput is maximized, but unnecessary operations consume power when mask bits are zero
Solution Approach 1:
The patent applies partial action by executing operations only on the subset of data elements indicated by active mask bits, rather than processing all elements. The clock gating mechanism enables or disables individual processing elements based on mask values, so that only necessary computations are performed. This partial execution approach eliminates wasted energy on operations that will be discarded while maintaining full throughput for the active subset of elements.
Data Source
AI summary
A processor includes an instruction schedule and dispatch (schedule/dispatch) unit to receive a single instruction multiple data (SIMD) instruction to perform an operation on multiple data elements stored in a storage location indicated by a first source operand. The instruction schedule/dispatch unit is to determine a first of the data elements that will not be operated to generate a result written to a destination operand based on a second source operand. The processor further includes multiple processing elements coupled to the instruction schedule/dispatch unit to process the data elements of the SIMD instruction in a vector manner, and a power management unit coupled to the instruction schedule/dispatch unit to reduce power consumption of a first of the processing elements configured to process the first data element.