Source Operand Collector Caching for Processor Latency
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Solution Overview
Problem
The configuration of crossbars in parallel processors requires multiple clock cycles to load operands from the register file into the datapath, introducing latency and limiting processing efficiency, as only one operand can be coupled to the datapath inputs per clock cycle.
Innovation Solution
Implementing a source operand collector caching method that decodes instructions to identify operands not stored in the cache, loads them from the local register file into the cache, and configures the processor core to execute instructions using cached operands, allowing multiple operands to be cached and reused across instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If crossbar configuration is used to load operands from register file to datapath, then operands can be transmitted, but it requires multiple clock cycles introducing latency
Solution Approach 1:
The operand collector pre-loads and caches source operands from the register file before they are needed by the execution unit. By anticipating and storing operands in advance, the system eliminates the need for time-critical crossbar configurations during instruction execution, thereby reducing processing latency without compromising operand delivery speed.
2Productivity
If crossbar is configured to couple one operand per clock cycle, then bandwidth is managed, but processing efficiency is limited
Solution Approach 1:
The operand collector creates copies of source operands from the register file and stores multiple copies in its cache structure. This allows the execution unit to access multiple operands simultaneously without requiring proportional bandwidth from the register file, thereby increasing operand throughput while maintaining manageable bandwidth requirements.
3Reliability
If operands are loaded from register file through crossbar, then data transmission is achieved, but bandwidth consumption increases
Solution Approach 1:
The operand collector serves as an intermediary buffer between the register file and the execution unit. It receives operands from the register file at relaxed bandwidth requirements and provides them to the execution unit on demand, thereby reducing the bandwidth burden on the register file-crossbar interface while ensuring reliable data transmission.
Data Source
AI summary
Methods and apparatus for source operand collector caching. In one embodiment, a processor includes a register file that may be coupled to storage elements (i.e., an operand collector) that provide inputs to the datapath of the processor core for executing an instruction. In order to reduce bandwidth between the register file and the operand collector, operands may be cached and reused in subsequent instructions. A scheduling unit maintains a cache table for monitoring which register values are currently stored in the operand collector. The scheduling unit may also configure the operand collector to select the particular storage elements that are coupled to the inputs to the datapath for a given instruction.