Content-Addressable Memory Linked Lists for In-Flight Hazard Ordering
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Solution Overview
Problem
Conventional microprocessors face memory hazards due to instructions operating on the same data without controlled atomic processing, leading to conflicts for access to limited resources, which existing linked lists fail to address efficiently with high hardware overhead.
Innovation Solution
A memory system with content-addressable entries that automatically establish and retire resource-based linked lists, allowing parallel searching and tracking of in-flight instances of access to resources, eliminating the need for external control circuits and reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional linked lists are used to order instructions for resource access, then instruction ordering and hazard avoidance are achieved, but hardware overhead and complexity increase
Solution Approach 1:
The content-addressable memory automatically performs the linked list operations without external control. When an instruction accesses a resource, the CAM entry self-organizes into the linked list structure by automatically comparing its resource address with existing entries and establishing sequential relationships, eliminating the need for external control logic that would otherwise be required to manage linked lists
Solution Approach 2:
The patent replaces the mechanical/structural approach of physical linked list pointers with content-addressable memory operations. Instead of using traditional pointer-based linked list structures that require complex interconnections, the system uses CAM's inherent parallel comparison capability to achieve the same ordering function with simpler hardware
2Ease of operation
If external control circuits are used to manage linked lists, then resource access ordering is achieved, but hardware requirements and overhead increase
Solution Approach 1:
The content-addressable memory performs multiple functions simultaneously: it stores resource addresses, compares incoming addresses against stored entries, determines linked list relationships, and manages the ordering of resource accesses. This multi-functionality eliminates the need for separate external control circuits that would otherwise be required to manage linked lists
Solution Approach 2:
The patent merges the linked list management functionality into the content-addressable memory structure itself. The CAM entries that store resource addresses also inherently provide the linked list ordering information through their content-addressable nature, combining what would traditionally be separate functions into a unified structure
3Adaptability or versatility
If traditional memory structures are used for tracking resource access, then resource ordering is achieved, but scalability and flexibility are limited
Solution Approach 1:
The linked list structure in the CAM is dynamic and can be modified on-the-fly as new resource addresses are accessed. The system can automatically adjust the linked list relationships by comparing new addresses with existing entries and inserting them in the appropriate sequential position, providing flexible adaptation without requiring reconfiguration of the underlying memory structure
Data Source
AI summary
A memory system with content-addressable entries supporting scalable, low overhead, in-fight establishment and retirement of resource-based linked lists, and related methods of operation and computer-readable media. The memory system can be used to track and establish an ordering of in-flight instances of access to a resource through a linked-list of content-addressable entries established in the memory system corresponding to such resource. Entries in the memory system that represent instances of access to a given resource can each be established as part of a linked list associated for the given resource to track a priority order for multiple instances of access the resource and then retired when an instance of access has been completed as part of a tracking system, such as to avoid hazards. The memory system provides a way to establish entries in a linked list for in flight instances of access to a resource for ordering and tracking.