Multi-Level Register File Bypass Controller for Processor Latency
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Solution Overview
Problem
As processors support more simultaneous threads and larger data word sizes, they face increased data access latency and power consumption due to larger register sets, which existing techniques like mirrored registers and multi-level register files only partially address.
Innovation Solution
A processor method that bypasses data from a first level register file to a second level register file, using storage locations for register mapping, allowing data to be loaded into storage locations designated for bypassing register mapping, and selecting these locations as input to the execution unit, thereby reducing latency and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of registers is increased to support more simultaneous threads and larger data word sizes, then the processor can support more threads and larger data sizes, but data access latency and power consumption increase
Solution Approach 1:
The register file is divided into multiple segments or levels. The patent implements a multi-level register file structure where frequently accessed registers are placed in lower-level, faster register files, while less frequently accessed registers are placed in higher-level, slower register files. This segmentation allows the processor to support a large total number of registers across all levels while maintaining fast access to the most critical registers.
Solution Approach 2:
Different parts of the register file have different access characteristics. The patent creates register files with varying access latencies and power consumption characteristics at different levels, matching the access patterns of different threads and instructions. Critical registers used by active threads are placed in low-latency register files, while less critical registers are placed in high-latency register files.
2Adaptability or versatility
If the number of registers is increased to support more simultaneous threads and larger data word sizes, then the processor can support more threads and larger data sizes, but power consumption increases
Solution Approach 1:
The register file is divided into multiple segments or levels. The patent implements a multi-level register file structure where frequently accessed registers are placed in lower-level, faster register files, while less frequently accessed registers are placed in higher-level, slower register files. This segmentation allows the processor to support a large total number of registers across all levels while maintaining fast access to the most critical registers.
Solution Approach 2:
Different parts of the register file have different access characteristics. The patent creates register files with varying access latencies and power consumption characteristics at different levels, matching the access patterns of different threads and instructions. Critical registers used by active threads are placed in low-latency register files, while less critical registers are placed in high-latency register files.
3Quantity of substance
If data is moved from first level register file to second level register file, then storage capacity is optimized, but data access latency increases
Solution Approach 1:
The system performs preliminary actions by predicting which data will be needed soon and keeping it in the first level register file, while moving data that is unlikely to be needed soon to the second level register file. The bypass mechanism is prepared in advance to quickly retrieve data from the second level register file when needed, preventing latency issues.
Solution Approach 2:
The bypass mechanism acts as an intermediary between the second level register file and the execution units. When data is needed that resides in the second level register file, the bypass mechanism quickly retrieves it and delivers it to the execution unit, effectively mediating the latency issue and making the second level register file accessible without the full penalty of its slower access time.
4Loss of time
If bypass storage locations are used to host data from second level register file, then data access latency is reduced, but device complexity increases
Solution Approach 1:
The bypass mechanism acts as an intermediary between the second level register file and the execution units. When data is needed that resides in the second level register file, the bypass mechanism quickly retrieves it and delivers it to the execution unit, effectively mediating the latency issue and making the second level register file accessible without the full penalty of its slower access time.
Solution Approach 2:
The bypass storage locations serve multiple functions: they act as a cache for data from the second level register file, provide quick access paths for critical data, and maintain mapping information for register allocation. This multi-functionality reduces the need for separate structures and minimizes overall system complexity.
Data Source
AI summary
A register file bypass controller in communication with a set of one or more bypass registers, the register file bypass controller configured to receive a register file bypass request; determine whether to grant the register file bypass request; determine whether data identified by the register file bypass request is present in the set of one or more bypass registers in response to determining to grant the register file bypass request; determine a selected bypass register in the set of one or more bypass registers in response to determining the data identified by the register file bypass request is not present in the set of one or more bypass registers; determine to store the data identified by the register file bypass request in the selected bypass register; and notify an execution unit to cancel instruction execution associated with the data identified by the register file bypass request.