Rotating Head Pointer Bypass Register File
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Solution Overview
Problem
Pipelined processor data paths require frequent copying of results through a bypass register file, leading to increased power usage and complex wiring due to the need for selecting among multiple storage locations.
Innovation Solution
A rotating head pointer system in the bypass register file allows results to remain in the same location until retirement, eliminating the need for constant copying and enabling a RAM-based implementation that simplifies wiring by sharing bit lines among entries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If results are copied through storage elements in the bypass register file each cycle, then the pipeline can stage results for N cycles, but power usage increases due to frequent copying operations
Solution Approach 1:
The patent applies a rotating head pointer mechanism that dynamically changes the write position in the bypass register file over time. Instead of copying data through N storage elements, the system uses a single write port with a rotating pointer that cycles through N positions, allowing the same physical storage location to be reused after N cycles. This dynamic approach eliminates frequent data copying while maintaining the pipeline staging capability.
Solution Approach 2:
The patent eliminates the need for physical data copying by using a rotating pointer index system. Rather than physically moving data through N storage elements, the system copies only the pointer value (an N-bit integer) and uses this pointer to access the appropriate storage location. This reduces the copying operation from moving entire data values to moving only small index values.
2Adaptability or versatility
If the processor can read from any of N+1 locations in the bypass register file, then functional units can access recent results, but the number of wires and wire tracks increases
Solution Approach 1:
The patent implements a universal read port design where a single read port can access any of the N storage locations by using an N-bit pointer value as the address. Instead of having N separate read ports or complex wiring for each location, the system uses one multi-functional read port that can be directed to any location through the rotating pointer mechanism, thereby reducing wiring complexity while maintaining access flexibility.
Solution Approach 2:
The rotating head pointer acts as an intermediary between the functional units and the N storage locations in the bypass register file. Instead of direct wiring from each functional unit to each storage location, the pointer serves as a mediator that receives the desired location information and directs the read port to the correct storage element, thereby reducing the number of wires and wire tracks required.
Data Source
AI summary
A processing bypass register file system and method are disclosed. In one embodiment a processing bypass register file includes a rotating head pointer, and a plurality of write ports, storage cells and read ports. The write ports receive processing result information. The head pointer identifies which entries are written by the write ports. The plurality of cells store the processing result information. The read ports forward results to the processing data path, and to an architectural register file for retirement.