Processor Retirement Logic Segmentation for Queue Entry Processing
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Solution Overview
Problem
In high-clock-frequency, high-performance systems, the complexity of retirement logic for processor load/store queues makes it difficult to retire entries at the rate of one per clock cycle, leading to bottlenecks due to increased complexity and decreasing clock periods.
Innovation Solution
Employing multiple retirement logic units to concurrently evaluate retirement conditions for queue entries, allowing each unit more time to process conditions, thereby enabling retirement of one entry per cycle by dividing the workload and using separate read pointers for even and odd entries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple retirement logic units are employed to concurrently evaluate retirement conditions, then the processing time per entry is reduced and retirement rate is improved, but the device complexity increases
Solution Approach 1:
The buffer is divided into two separate sub-buffers (even entries and odd entries), and the retirement logic is segmented into multiple independent retirement logic units. Each unit evaluates retirement conditions for a specific subset of entries concurrently, reducing the processing time per entry while maintaining overall system functionality.
Solution Approach 2:
The patent introduces a new dimension of parallelism by employing multiple retirement logic units operating simultaneously on different entry subsets. This transforms the single-threaded retirement process into a multi-threaded concurrent evaluation system, effectively doubling the retirement throughput.
2Speed
If the clock frequency is increased to improve processor speed, then the processing capacity is improved, but the time available to evaluate retirement conditions is reduced
Solution Approach 1:
By segmenting the buffer into even and odd entry sub-buffers and assigning dedicated retirement logic units to each, the evaluation workload is distributed across multiple units operating in parallel. This allows each unit to complete its evaluation within the reduced clock period while maintaining the overall retirement rate.
Solution Approach 2:
The retirement conditions are evaluated concurrently for multiple entries in parallel rather than sequentially. This preliminary concurrent evaluation ensures that all necessary checks are completed within the available clock period before retirement decisions are made.
3Reliability
If complex retirement conditions are implemented to handle more scenarios, then the reliability and correctness are improved, but the logic depth and processing time increase
Solution Approach 1:
The complex retirement condition evaluation is segmented across multiple independent retirement logic units, each handling a specific subset of entries. This distribution reduces the logic depth within each unit while maintaining the comprehensive evaluation of all retirement conditions through parallel processing.
Data Source
AI summary
Systems and methods for determining whether to retire a data entry from a buffer using multiple retirement logic units. In one embodiment, each retirement unit concurrently evaluates retirement conditions for one of the buffer entries in an associated subset (e.g., even or odd) of the buffer. Selection logic coupled to the retirement units alternately selects the first or second retirement unit for retirement of one of the entries in the associated subset. Because the aggregate number of entries retired by the combined retirement logic units is divided by the number of retirement logic units, each retirement logic unit has more time to process the retirement conditions for corresponding queue entries. The buffer may be any of a variety of different types of buffers and may comprise a single buffer, or multiple buffers.