uOp Buffer Loop Mode for Processor Power Reduction
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Solution Overview
Problem
Processor architectures face inefficiencies in power consumption due to the conventional method of fetching and decoding instructions for each instance of an instruction in a program order, especially during loop execution, which leads to unnecessary power usage in stages like the fetch and decode stages.
Innovation Solution
Employing a micro-operation (uOp) buffer and an instruction byte buffer that enter loop modes to suspend operations outside the loop, allowing repeated dispatch of stored uOps and instruction bytes only, thereby reducing power consumption by suppressing accesses to the fetch and decode stages during loop execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If instructions are fetched and decoded for each instance in program order, then instruction execution is maintained, but power consumption increases
Solution Approach 1:
The patent pre-fetches and decodes instructions into micro-operations before they are needed for execution. During loop execution, the pre-decoded micro-operations are reused multiple times without re-fetching and re-decoding, thereby eliminating redundant operations and reducing power consumption while maintaining execution efficiency
Solution Approach 2:
The patent creates copies of decoded micro-operations in a buffer that can be reused for multiple loop iterations. Instead of repeatedly fetching and decoding the same instructions, the system copies the micro-operations to an execution buffer and reuses them, significantly reducing the workload on fetch and decode stages and lowering power consumption
2Loss of energy
If fetch and decode stages operate continuously, then instruction processing is maintained, but unnecessary power is consumed during loop execution
Solution Approach 1:
The patent dynamically adjusts the operation of fetch and decode stages based on detection of loop structures. When a loop is detected, the system suspends or reduces activity in these stages since the instructions will be reused from the buffer, and resumes them when exiting the loop, thereby adapting power consumption to actual processing needs while maintaining reliability
Solution Approach 2:
The system uses loop detection mechanisms that provide feedback about upcoming repetitive instruction sequences. This feedback allows the fetch and decode stages to be selectively suspended or throttled during loop execution, preventing unnecessary power consumption while ensuring instructions are available when needed through the pre-filled buffer
Data Source
AI summary
In a normal, non-loop mode a uOp buffer receives and stores for dispatch the uOps generated by a decode stage based on a received instruction sequence. In response to detecting a loop in the instruction sequence, the uOp buffer is placed into a loop mode whereby, after the uOps associated with the loop have been stored at the uOp buffer, storage of further uOps at the buffer is suspended. To execute the loop, the uOp buffer repeatedly dispatches the uOps associated with the loop's instructions until the end condition of the loop is met and the uOp buffer exits the loop mode.