Host Controller Cache for SATA Command Header Storage
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Solution Overview
Problem
Current SATA systems lack hardware support for simultaneous switching across all devices, leading to inefficiencies and increased latency due to the need for frequent memory fetches.
Innovation Solution
Implementing a cache memory within the chipset to enable efficient switching of commands across multiple SATA devices, reducing die size and latency by storing command information and using intelligent caching policies to manage cache entries effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a cache memory is implemented in the host controller, then switching efficiency and performance are improved, but device complexity and die size increase
Solution Approach 1:
The cache memory is segmented into multiple entries, each capable of storing command header information for different devices. This segmentation allows the host controller to manage multiple devices efficiently by dividing the cache into manageable units, improving switching efficiency without requiring a monolithic complex structure.
Solution Approach 2:
The cache memory stores command header information in advance before commands are actually executed. This preliminary storage of command headers allows the host controller to quickly retrieve necessary information when switching between devices, improving performance by eliminating the need for frequent memory fetches during the switching process.
2Loss of time
If command header information is stored in cache memory, then data transfer latency is reduced, but manufacturing cost and die area increase
Solution Approach 1:
Only the essential command header information is extracted and stored in the cache memory, rather than storing complete command data. This selective extraction reduces the amount of data that needs to be cached, thereby reducing die area and manufacturing cost while still achieving the latency reduction benefit for critical command header operations.
Solution Approach 2:
The cache memory is implemented with specific storage characteristics tailored to the command header information - using appropriate data types, storage formats, and access patterns optimized for command header operations. This localized optimization ensures that the cache provides maximum benefit for command header storage while minimizing the overall resource consumption and manufacturing complexity.
3Productivity
If hardware support for simultaneous switching is provided for all devices, then FBS performance is improved, but device complexity and hardware resources increase
Solution Approach 1:
The cache memory acts as an intermediary between the host controller and the devices. By storing command header information in the cache, the host controller can efficiently manage simultaneous switching to multiple devices without requiring complex hardware support for all devices at once. The cache mediates the switching process, allowing FBS performance improvement with reduced hardware complexity.
Data Source
AI summary
In one embodiment, the present invention includes a host controller having a cache memory to store entries each including, at least, a command header (CH) portion having data associated with a command from the host controller to one of multiple devices coupled to a port multiplier, and a physical region descriptor (PRD) portion to store address information associated with a next address for data transfer with regard to the command. Other embodiments are described and claimed.