Memory Access Circuit With Prefetching for DSP Latency Hiding
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Solution Overview
Problem
Modern digital signal processors face challenges such as increasing workloads, memory system latency, and limited bandwidth, which are exacerbated by the complexity of systems on a chip and the in-order nature of central processing units, leading to subpar performance and scalability issues.
Innovation Solution
The integration of streaming engines with vector support, scoreboarded loads, speculative loads, and software-directed prefetch, along with a credit-based bidirectional bus protocol, enhances memory system efficiency and coherence, allowing for improved bus utilization and data transfer rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the bus width and clock rate are increased to increase bandwidth, then the bandwidth is improved, but the latency increases and routing issues worsen
Solution Approach 1:
The patent implements a prefetching mechanism that retrieves data from memory before it is actually needed by the processor. The prefetcher monitors memory access patterns and initiates data transfer in advance, storing prefetched data in buffer memory. This preliminary action eliminates the need to wait for memory operations during normal processing, effectively hiding memory latency without requiring wider buses or higher clock rates.
2Loss of time
If deeper buffering is implemented to hide latency, then the latency penalty is reduced, but the device complexity increases
Solution Approach 1:
The patent implements a self-service buffering system where the buffer memory automatically manages its own content based on observed memory access patterns. The prefetcher monitors which memory addresses are being accessed and autonomously decides what data to prefetch and when, without requiring complex external control logic. This self-managing approach reduces the overall system complexity while still providing effective latency hiding through intelligent buffering.
3Ease of operation
If the CPU operates in-order to maintain simplicity, then the ease of operation is improved, but the ability to hide latency is reduced
Solution Approach 1:
The patent introduces a prefetcher as an intermediary component between the in-order CPU and the memory system. This prefetcher acts as a mediator that proactively retrieves data and places it in buffer memory ahead of time, allowing the simple in-order CPU to access data without stalling. The intermediary handles the complexity of latency management separately from the CPU core, preserving CPU simplicity while effectively hiding memory latency.
Data Source
AI summary
Disclosed embodiments include an electronic device having a processor core, a memory, a register, and a data load unit to receive a plurality of data elements stored in the memory in response to an instruction. All of the data elements hare the same data size, which is specified by one or more coding bits. The data load unit includes an address generator to generate addresses corresponding to locations in the memory at which the data elements are located, and a formatting unit to format the data elements. The register is configured to store the formatted data elements, and the processor core is configured to receive the formatted data elements from the register.