Nonvolatile CAM Segmented Power Switching
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Solution Overview
Problem
SRAM-based content addressable memory (CAM) cells are volatile, leading to high power consumption due to leakage current during standby periods, and shutting off power results in data loss, requiring frequent and power-intensive data transfer to non-volatile storage.
Innovation Solution
A nonvolatile CAM with segmented word circuits using power switches to turn off power during standby and turn on only as needed during search operations, employing nonvolatile storage elements like magnetic tunnel junctions to maintain data without power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power is shut off to reduce power consumption during standby, then power consumption is reduced, but data is lost
Solution Approach 1:
The CAM cell is divided into two independent storage elements: a nonvolatile storage element (first storage element) that retains data without power, and a volatile storage element (second storage element) that enables fast search operations. This segmentation allows the system to maintain data integrity during standby while enabling high-speed operation when powered.
Solution Approach 2:
The patent changes the storage state parameter from purely volatile (SRAM) to a hybrid state using nonvolatile memory. The nonvolatile storage element maintains data in a stable magnetic or resistive state that persists without power, fundamentally changing how data is preserved during standby periods.
2Speed
If all storage words are activated for parallel comparison, then search speed is high, but operating power is very high
Solution Approach 1:
The word circuit is divided into multiple segments, each with its own power switch. This allows selective activation of only those segments containing potential match candidates, rather than activating all storage words simultaneously. The segmentation enables partial parallel comparison, reducing power consumption while maintaining search functionality.
Solution Approach 2:
The patent introduces dynamic power control where power switches adjust the active state of storage segments based on search results. During search operations, power is dynamically allocated to active segments only, allowing the system to adapt power consumption to the actual search needs rather than maintaining constant high power for all segments.
3Reliability
If data is transferred to nonvolatile storage before power shutdown, then data integrity is maintained, but waiting time and complexity increase
Solution Approach 1:
The memory cell is segmented into nonvolatile and volatile storage elements that work together. The nonvolatile element continuously maintains data without requiring transfer operations, eliminating the complexity of data movement while ensuring data integrity during power transitions.
Solution Approach 2:
The nonvolatile storage element automatically maintains data retention without requiring external intervention for data transfer or protection. The magnetic tunnel junction or resistive switching element inherently preserves data state, making the system self-sufficient for data protection during standby and power transitions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces power consumption during search operations and standby periods while maintaining data integrity, eliminating the need for frequent data transfers and reducing operational complexity.
Implementation Method 1
Each of the one or more memory cells includes a nonvolatile storage element... employing nonvolatile storage elements like magnetic tunnel junctions to maintain data without power
Data Source
AI summary
Provided is a nonvolatile content addressable memory. Each word circuit includes a plurality of segments having an order relation. Each of the segments includes one or more memory cells. Each of the memory cells includes a nonvolatile storage element. Each of the segments includes a power switch for turning on/off a power of a memory cell of the segment. During stand-by, all the power switches are turned off, and, in search operation, the power switch is turned on as necessary for each of the segments.