Multibank Register File Thread Identifier Access
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Solution Overview
Problem
Multithreaded processors face challenges in managing register files due to increased processor die area, power consumption, and design complexity as the number of threads increases, requiring efficient organization to minimize context-switching overhead and resource allocation.
Innovation Solution
A processor architecture with a register file organized into banks corresponding to thread identifiers and register windows, allowing for efficient retrieval and storage of operands across multiple threads, reducing the number of read and write ports needed, and dynamically allocating resources among threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate copy of architectural state is implemented for each executing thread, then context-switching overhead is avoided, but processor die area increases
Solution Approach 1:
The register file is segmented into multiple banks, where each bank can be independently accessed. This segmentation allows different threads to access different banks simultaneously, reducing the need for complete architectural state copies while maintaining low context-switching overhead.
Solution Approach 2:
The patent introduces a new dimension of organization by arranging register entries in a three-dimensional structure: banks (spatial division), threads (temporal multiplexing), and register identifiers (functional organization). This multi-dimensional organization allows efficient access patterns that reduce both die area and context-switching overhead.
2Reliability
If a separate copy of architectural state is implemented for each executing thread, then context-switching overhead is avoided, but power consumption increases
Solution Approach 1:
The register file banks are designed to serve multiple threads simultaneously, making them universal resources rather than dedicated copies. This multi-functionality reduces the total number of storage elements needed, thereby reducing power consumption while maintaining the ability to serve multiple threads with minimal context-switching overhead.
Solution Approach 2:
By segmenting the register file into banks that can be selectively activated for different threads, the system avoids powering up complete architectural state copies for all threads simultaneously. Only the necessary banks are activated based on current thread execution needs, reducing overall power consumption.
3Reliability
If a separate copy of architectural state is implemented for each executing thread, then context-switching overhead is avoided, but design complexity increases
Solution Approach 1:
The register file is divided into independent banks with standardized interfaces, which simplifies the overall design by breaking down the complex task of managing architectural state into smaller, manageable units. Each bank follows the same structure, reducing design complexity through repetition and standardization.
Solution Approach 2:
The patent organizes the register file along multiple dimensions (banks, threads, register identifiers), which provides a systematic framework for managing architectural state. This multi-dimensional organization creates regular patterns in the design, making it easier to implement and verify compared to irregular full copies of architectural state for each thread.
4Area of stationary object
If register file size is reduced, then processor die area and power consumption decrease, but computational throughput may be affected
Solution Approach 1:
The segmented bank structure allows multiple threads to access different banks in parallel, maintaining high computational throughput despite the reduced size of individual banks. The segmentation enables spatial parallelism that compensates for the smaller register file capacity.
Solution Approach 2:
The register file design ensures continuous useful action by allowing different threads to simultaneously utilize different banks, maximizing the utilization of the reduced register file capacity. This continuous parallel access maintains high computational throughput without requiring larger register files.
Data Source
AI summary
A processor includes an instruction fetch unit configured to issue instructions for execution, where the instructions are selected from a number of threads, where each given instruction has a corresponding thread identifier, and where at least some of the instructions specify operand(s) via register identifiers. A register file stores operands usable by the instructions, and may include several banks, each corresponding to a register identifiers and including several entries corresponding to the several threads, wherein the entries are configured to store data values. In response to receiving a request to read a particular register identifier for a given thread identifier, the register file may be configured to decode the given thread identifier to retrieve entries from the banks that correspond to the given thread identifier. The register file may further select, from among the retrieved entries, a data value corresponding to the particular register identifier to be output.