Fully Associative Banking for Memory Context Switching Latency
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Solution Overview
Problem
Memory devices face performance degradation due to redundant information sent during multiple address cycles and context switching among software threads, which increases latency and reduces efficiency.
Innovation Solution
A system utilizing row address buffers and row data buffers to store high-order addresses and associated data, allowing for efficient access by caching frequently accessed memory regions and implementing a replacement policy to manage buffer availability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a narrow address bus is used to reduce the number of pins, then the external bus is simplified, but multiple address cycles are required increasing latency
Solution Approach 1:
The patent pre-loads row addresses into dedicated row address buffers before data access is needed. By anticipating and storing high-order address bits in advance, the system eliminates the need for multiple address cycles, directly reducing access latency while maintaining a narrow address bus structure.
Solution Approach 2:
The patent divides the address buffer into multiple segments (row address buffers and row data buffers) that can be independently managed. This segmentation allows simultaneous preparation of address information in one buffer while data is being accessed from another, overlapping operations to reduce overall latency.
2Speed
If a cache is used to store frequently accessed memory portions, then access speed is improved, but context switching causes flushing and reloading increasing latency
Solution Approach 1:
The patent implements self-service mechanisms where the buffer replacement policy automatically determines which buffer entries to retain or flush based on current access patterns, without requiring complete buffer invalidation during context switches. The system serves itself by maintaining relevant address-data associations across context boundaries.
Solution Approach 2:
The patent changes the state parameters of buffers by implementing different buffer replacement policies (LRU, FIFO, random) that adapt to different workload characteristics. By dynamically adjusting buffer management parameters rather than using a fixed cache structure, the system maintains performance across varying context switching scenarios.
3Device complexity
If redundant address information is sent during multiple address cycles, then the narrow bus requirement is met, but performance decreases due to increased latency
Solution Approach 1:
The patent performs preliminary loading of row addresses into dedicated buffers before data access operations. By pre-establishing the address-to-buffer mapping, the system eliminates redundant address transmissions during data access cycles, improving performance while maintaining a simple narrow bus structure for address input.
Solution Approach 2:
The patent creates copies of the high-order address bits and stores them in row address buffers. Instead of repeatedly transmitting the full address through the narrow bus, the system copies and caches the critical address portions, allowing rapid data access without redundant bus transactions.
4Speed
If buffers are tied to specific row addresses, then access efficiency is improved, but buffer availability decreases requiring replacement policies
Solution Approach 1:
The patent implements dynamic buffer management where the association between row address buffers and specific addresses can change over time based on access patterns. The buffers transition from static fixed assignments to dynamic reconfigurable associations, allowing the system to adapt to different workloads while maintaining efficient access to currently active address regions.
Solution Approach 2:
The patent changes the binding parameters of buffers by implementing replacement policies that modify which address is associated with which buffer. By dynamically adjusting these parameters based on LRU, FIFO, or random criteria, the system balances access efficiency with buffer availability, ensuring that buffers remain versatile while maintaining efficient access to active data.
Data Source
AI summary
A system is provided that facilitates read access in a memory device. The system comprises a plurality of row addresses buffers that store high order addresses associated with one or more software threads. The system further comprises a plurality of row data buffers. The row data buffers are each associated with at least one row address buffer and store row data within the range of the high order addresses of the row address buffers. The system increase memory device performance by limiting the latency associated with context switching. The plurality of row address buffers and row data buffers enables software threads to associate with one or more buffers and maintain efficient subsequent memory accesses despite context switching.