Program Counter Range Comparison Circuit
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Solution Overview
Problem
In microprocessor applications, comparing values within a range is costly and detrimental to processor performance due to the need for multiple comparisons across a wide range of values, especially in superscalar CPUs where signal increments are high, leading to inefficiencies in determining program counter values and generating control signals.
Innovation Solution
A circuit and method that examine whether a value from a first range is equal to or greater than the lower boundary of a second range, and whether the lower boundary of the first range is smaller than or equal to the upper boundary of the second range, using a combination of comparators and arithmetic logic to simplify the comparison process by dividing it into partial inequations and focusing on boundary value examinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a set of comparators is used to determine whether the CPU has executed instructions within a certain PC range, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the PC value comparison into two separate comparison operations: first comparing the lower boundary of the PC range with the lower boundary of the target range, and second comparing the upper boundary of the PC range with the upper boundary of the target range. This segmentation reduces the complexity of a single complex comparator by dividing it into simpler comparison stages.
Solution Approach 2:
The patent performs partial comparisons by examining only the boundary values of the PC range rather than comparing every possible PC value against the target range. This partial action approach maintains measurement precision for range detection while significantly reducing the computational burden and circuit complexity.
2Measurement precision
If multiple comparisons are performed for each calculated PC value, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent performs partial comparisons by examining only the boundary values of the PC range rather than comparing every possible PC value against the target range. This partial action approach maintains measurement precision for range detection while significantly reducing the computational burden and circuit complexity.
Solution Approach 2:
The patent performs preliminary comparisons of boundary values before full PC value comparison is needed. By pre-establishing the relationship between boundary values, the system avoids performing multiple redundant comparisons for each individual PC value, thereby improving throughput while maintaining accuracy.
3Productivity
If comparison operations are performed in the same clock cycle, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent segments the comparison operation into two independent comparison stages that can be performed in parallel within the same clock cycle. The first comparison evaluates the lower boundary relationship while the second comparison evaluates the upper boundary relationship, allowing simultaneous execution without requiring complex sequential control logic.
Data Source
AI summary
A circuit and a method of examining in a microprocessor a section of a first range of values and a second range of values each comprising a lower boundary value and an upper boundary value is disclosed. The method includes examining whether a value of the first range of values is equal to or greater than the lower boundary value of the second range of values, and examining whether the lower boundary value of the first range of values is smaller than or equal to the upper boundary value of the second range of values.