Cache Assist Controller Zero Fill for Processor Efficiency
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Solution Overview
Problem
In processor systems, cache misses lead to inefficient performance due to the need to fetch data from lower-level memory, even when the data is intended to be overwritten, wasting processor cycles.
Innovation Solution
A cache assist controller is introduced that returns zero fill for memory addresses identified by the processor core as intended for overwrite, eliminating the need for data fetching in such cases and improving processor efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is fetched from lower-level memory during cache miss, then cache data completeness is improved, but processor cycles are wasted when data is intended to be overwritten
Solution Approach 1:
The system performs preliminary action by having the processor core indicate upcoming write operations to the cache assist controller before the actual write occurs. This allows the cache assist controller to pre-identify which memory addresses will be overwritten, so when cache misses occur for these addresses, zero fill can be returned immediately without fetching data from lower-level memory, thus saving processor cycles while maintaining data completeness for non-overwritten addresses
Solution Approach 2:
The cache assist controller serves as an intermediary between the processor core and the cache controller. It receives write operation information from the processor core, determines which addresses will be overwritten, and provides this information to the cache controller. This intermediary layer enables the system to distinguish between cache misses that require data fetching and those that can be efficiently handled with zero fill, resolving the contradiction between data completeness and processor cycle efficiency
2Productivity
If zero fill is returned for cache misses, then processor efficiency is improved, but data fetching is eliminated even when data might be needed
Solution Approach 1:
The system implements feedback by having the processor core continuously provide information about upcoming write operations to the cache assist controller. This feedback loop ensures that the cache assist controller has accurate, up-to-date information about which memory addresses will be overwritten. Based on this feedback, the cache assist controller can make informed decisions about whether to return zero fill or trigger actual data fetching, thus maintaining processor efficiency while ensuring data fetching accuracy when truly needed
Data Source
AI summary
A processor system includes a processor core, a cache, a cache controller, and a cache assist controller. The processor core issues a read/write command for reading data from or writing data to a memory. The processor core also outputs an address range specifying addresses for which the cache assist controller can return zero fill, e.g., an address range for the read/write command. The cache controller transmits a cache request to the cache assist controller based on the read/write command. The cache assist controller receives the address range output by the processor core and compares the address range to the cache request. If a memory address in the cache request falls within the address range, the cache assist controller returns a string of zeroes, rather than fetching and returning data stored at the memory address.