N-way Cache Way Prediction for Power Reduction
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Solution Overview
Problem
Conventional microprocessor data caches consume significant power and generate heat, making them impractical for many System-on-chip (SoC) applications, despite providing performance advantages.
Innovation Solution
A microprocessor with an N-way cache system that uses way prediction logic to selectively enable and disable cache components, predicting the cache way where data is stored and applying an enabling signal only to the predicted way, thereby reducing power consumption by inhibiting the remaining cache ways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional caches are used to reduce latency, then data access speed is improved, but power consumption increases significantly
Solution Approach 1:
The cache is divided into multiple independent ways, and the patent selectively enables only the predicted active way while disabling other ways. This segmentation allows the cache to maintain low-latency access for the active way while reducing overall power consumption by keeping other ways in a low-power state.
Solution Approach 2:
The patent dynamically enables and disables cache ways based on way prediction. The enable signal is dynamically controlled by the way prediction logic to activate only the predicted active way, making the cache configuration adaptive rather than static, thus reducing power consumption while maintaining performance.
2Reliability
If all cache ways are enabled to ensure data availability, then access reliability is improved, but heat generation increases
Solution Approach 1:
Instead of enabling all cache ways, the patent enables only the predicted active way (partial action). This partial enabling strategy maintains data availability for the predicted access while avoiding the heat generation associated with keeping all ways active, thus resolving the contradiction between reliability and temperature.
3Use of energy by moving object
If way prediction logic is added to selectively enable cache ways, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The way prediction logic performs preliminary prediction of which cache way will be accessed before the actual cache access occurs. This preliminary action allows the system to pre-enable only the predicted active way, reducing power consumption without requiring complex runtime control logic for all cache ways.
Data Source
AI summary
A microprocessor includes one or more N-way caches and a way prediction logic that selectively enables and disables the cache ways so as to reduce the power consumption. The way prediction logic receives an address and predicts in which one of the cache ways the data associated with the address is likely to be stored. The way prediction logic causes an enabling signal to be supplied only to the way predicted to contain the requested data. The remaining (N−1) of the cache ways do not receive the enabling signal. The power consumed by the cache is thus significantly reduced.