Parallel CXL RAS Channels for Faster Error Isolation
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Solution Overview
Problem
Conventional memory devices with multiple memory media lack efficient RAS channel management, leading to issues like inability to quickly identify error-causing devices, head-of-line blocking, and inefficient bandwidth utilization due to fixed ECC granularity, resulting in reduced responsiveness and increased latency.
Innovation Solution
Implementing parallel RAS channels with dedicated datapaths and caches for each group of memory media devices, along with virtual channels for independent flow control and differentiated quality of service, allowing for finer traffic throttling and improved responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple memory media devices are connected to the same device, then storage capacity and bandwidth are improved, but error detection time increases and link bandwidth is reduced due to inability to control ECC granularity
Solution Approach 1:
The patent divides the memory system into multiple independent RAS channels, each handling specific memory media devices. This segmentation allows parallel error detection and correction operations across different channels, reducing the overall error detection time while maintaining support for multiple memory devices.
Solution Approach 2:
The patent introduces a new dimension of control by implementing separate RAS channels with independent ECC control for each memory media device or group. This enables granular control over error correction operations, allowing the system to process ECC for individual devices independently rather than as a bulk operation, thus reducing error detection time.
2Quantity of substance
If multiple memory media devices are connected to the same device, then storage capacity is improved, but link bandwidth is reduced due to inability to control ECC granularity
Solution Approach 1:
By segmenting the memory interface into multiple RAS channels, each channel can independently manage ECC operations for its assigned memory devices. This prevents ECC processing in one channel from blocking data transfer in other channels, thereby maintaining higher overall link bandwidth while supporting multiple memory devices.
Solution Approach 2:
The patent adds a channel dimension to the memory interface architecture, creating parallel pathways for data and ECC operations. This allows simultaneous ECC processing and data transfer across different channels, effectively increasing the usable link bandwidth while maintaining support for multiple memory media devices.
3Reliability
If RAS features are implemented in conventional memory devices, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent implements RAS functionality through segmented RAS channels that are integrated into the existing memory controller architecture. Each RAS channel handles specific memory devices independently, allowing reliability features to be added without requiring a complete redesign of the memory system, thus limiting the increase in device complexity.
4Speed
If parallel RAS channels are implemented, then responsiveness to data requests is improved and congestion is reduced, but device complexity increases
Solution Approach 1:
The patent divides the memory controller into multiple RAS channels that can independently process data requests. This segmentation enables parallel handling of multiple memory operations, improving responsiveness and reducing congestion. The modular channel-based architecture allows for scalable implementation, adding complexity only to the extent necessary to achieve the performance benefits.
Data Source
AI summary
A memory device comprises a plurality of backend interfaces that are each configured to connect to a respective media device (e.g., DDR, LPDDR DRAM), a plurality of reliability, availability and serviceability (RAS) channel datapaths with each RAS channel datapath connected to one or more backend interfaces, one or more caches that are each connected to at least one RAS channel datapath, and control circuitry. The control circuitry is configured to: in response to receiving a memory access request for a memory location, search a cache of the one or more caches for the requested memory location; and when, in response to the search, the requested memory location is not found in the cache, obtain the requested memory location from a media device connected to the at least one RAS channel datapath. Corresponding methods are also described.