Pipeline Control Preload Predictor Reducing Stall Cycles
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Solution Overview
Problem
In instruction pipeline architectures, load-use instruction pairs cause stalls due to delayed data access from cache memories, leading to performance issues, especially with deeper pipeline stages.
Innovation Solution
An apparatus and method utilizing a preload predictor and a data buffer to pre-fetch and store data from cache memories, allowing faster access for subsequent load instructions, thereby reducing stall cycles and improving pipeline performance without significant additional costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If deeper pipeline stages are used to achieve higher clock rates, then CPU clock rate is improved, but pipeline performance deteriorates due to increased severity of load-use stalls
Solution Approach 1:
The patent applies preliminary action by implementing a data buffer that pre-loads data from cache memory before it is actually needed by the ALU. When a load instruction is detected, the system proactively fetches the data and stores it in the data buffer in advance, so that subsequent instructions can access the data immediately without stalling the pipeline. This preliminary data preparation eliminates the performance penalty that would normally accompany deeper pipeline stages.
2Quantity of substance
If data is fetched from cache memory, then data storage capacity is improved, but data access speed deteriorates causing execution delays
Solution Approach 1:
The patent applies segmentation by dividing the data storage hierarchy into distinct segments: cache memory for bulk storage and a specialized data buffer for high-speed access. The data buffer acts as an intermediate segment between the cache and the ALU, holding frequently accessed data in a form that enables rapid retrieval. This segmentation allows the system to maintain large storage capacity in the cache while providing fast access paths through the buffer for critical data.
3Productivity
If load instructions are executed, then data loading capability is improved, but pipeline schedule deteriorates due to required execution cycles
Solution Approach 1:
The patent applies continuity of useful action by ensuring that the data buffer is continuously populated with data from cache memory as load instructions are executed. Rather than allowing the pipeline to stall and idle during data transfer operations, the system maintains continuous productive work by pre-loading data into the buffer during cycles when the ALU is performing other operations. This eliminates gaps in the pipeline schedule and maintains continuous useful action throughout the system.
Data Source
AI summary
An apparatus and a method for pipeline control are provided. The apparatus includes a preload predictor, an arithmetic logic unit (ALU) and a data buffer. The preload predictor is configured to determine whether a load instruction conforms to at least one specific condition, to generate a preload determination result. The ALU is configured to perform arithmetic logic operations, and the data buffer is configured to provide data for being used by the ALU. When the preload determination result indicates that the load instruction conforms to the at least one specific condition, the data buffer fetches preload data from a cache memory according to information carried by the load instruction and stores the preload data in the data buffer, where the preload data is data requested by a subsequent load instruction.