Register Rename Unit Partial Access for Power Reduction
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Solution Overview
Problem
The increasing power consumption in mobile devices due to register file accesses, particularly when dealing with varying data types that do not utilize the full width of a general-purpose register, leads to unnecessary energy expenditure.
Innovation Solution
A processor with a register rename unit that assigns identifiers to destination operands and detects instructions associated with non-full-width data types, preventing access to the unused portions of physical registers during read and write operations, and using bypass logic to convey numerical values for the inaccessible parts, such as zero, to reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If full width register accesses are performed for all instructions, then data access simplicity is maintained, but power consumption increases unnecessarily
Solution Approach 1:
The register file is segmented into multiple banks (e.g., even and odd banks), and the access control is segmented to selectively enable only the necessary portions of registers based on instruction data type. This allows partial register accesses instead of always accessing the full register width, thereby reducing power consumption while maintaining architectural simplicity.
Solution Approach 2:
The register access width is made dynamic rather than static. The access control logic dynamically determines the actual data width being accessed (e.g., 32-bit vs 64-bit) and enables only the corresponding portion of the register file, allowing the system to adapt to different data type sizes and reduce unnecessary power consumption.
2Adaptability or versatility
If register file width is increased to support larger data types, then data model capacity is improved, but power consumption for accessing unused portions increases
Solution Approach 1:
Different portions of the register file are activated based on the local requirements of each instruction. When a 32-bit instruction is executed, only the lower 32 bits of the register are accessed, while the upper 32 bits remain inactive. This local quality approach ensures that the register file supports large data types when needed but consumes minimal power when smaller data types are used.
Solution Approach 2:
The effective width parameter of register accesses is changed dynamically based on the instruction being executed. The access control logic modifies the access width parameter from the full register width (e.g., 64 bits) to the actual data width required (e.g., 32 bits), thereby supporting versatile data models while optimizing power consumption for each specific operation.
3Ease of operation
If full register width is always accessed, then read simplicity is maintained, but unnecessary power is consumed for unused register portions
Solution Approach 1:
Instead of performing excessive action by always accessing the full register width, the system performs partial action by accessing only the necessary portion of the register. The access control logic determines the exact width needed and enables only that portion, eliminating unnecessary power consumption while maintaining ease of operation through automated width detection and control.
Data Source
AI summary
A system and method for efficiently reducing the power consumption of register file accesses. A processor is operable to execute instructions with two or more data types, each with an associated size and alignment. Data operands for a first data type use operand sizes equal to an entire width of a physical register within a physical register file. Data operands for a second data type use operand sizes less than an entire width of a physical register. Accesses of the physical register file for operands associated with a non-full-width data type do not access a full width of the physical registers. A given numerical value may be bypassed for the portion of the physical register that is not accessed.