Cache Controller Non-blocking Memory Operations
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Solution Overview
Problem
Conventional memory transfer operations in computer systems, such as those using programmed input/output (PIO) and direct memory access (DMA), consume processor bus bandwidth and lead to delays and reduced performance due to the need for bus contention and inconsistent data states during transfers.
Innovation Solution
A cache controller that manipulates cache mappings independently of data operations, allowing for non-blocking memory operations like move, copy, zero, deprioritize, and invalidate, which reduce the need for bus bandwidth and processor cycles by remapping cache blocks and altering data maintenance strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional memory transfer operations (PIO or DMA) are used, then data can be transferred between memory and I/O devices, but processor bus bandwidth is consumed and processor performance is reduced due to bus contention
Solution Approach 1:
The patent introduces a cache controller as an intermediary device between the processor and main memory. The cache controller independently manages data transfers between cache and main memory without requiring processor intervention or bus access. This mediator handles memory operations in parallel with processor execution, eliminating bus contention and allowing the processor to continue executing instructions without waiting for memory operations to complete.
Solution Approach 2:
The patent segments the memory system into multiple independent components: processor, cache memory, cache controller, and main memory. The cache controller is given independent control authority to manage data transfers between cache and main memory, separating this function from the processor's control responsibilities. This segmentation allows memory operations to proceed independently without blocking the processor bus.
2Productivity
If cache operations are performed using conventional methods, then data can be cached in memory blocks, but bus bandwidth is consumed and data inconsistency issues arise during transfers
Solution Approach 1:
The cache controller serves as an intermediary that maintains data consistency between cache and main memory. It independently manages data transfers and tracking, ensuring that data in the cache remains consistent with main memory without requiring processor involvement. The cache controller uses tracking structures to monitor which main memory addresses are cached and manages data coherence autonomously.
Solution Approach 2:
The patent implements feedback mechanisms where the cache controller continuously monitors and tracks which main memory addresses are currently cached. This feedback information is used to make intelligent decisions about data transfers, eviction policies, and consistency maintenance. The tracking structures provide real-time information about cache state, enabling the controller to prevent data inconsistency and optimize memory operations.
Data Source
AI summary
A cache controller in a computer system is configured to manage a cache such that the use of bus bandwidth is reduced. The cache controller receives commands from a processor. In response, a cache mapping maintaining information for each block in the cache is modified. The cache mapping may include an address, a dirty bit, a zero bit, and a priority for each cache block. The address indicates an address in main memory for which the cache block caches data. The dirty bit indicates whether the data in the cache block is consistent with data in main memory at the address. The zero bit indicates whether data at the address should be read as a default value, and the priority specifies a priority for evicting the cache block. By manipulating this mapping information, commands such as move, copy swap, zero, deprioritize and deactivate may be implemented.