CXL HDM Decoder Sequencing With Virtual Decoders for Lower Area
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Solution Overview
Problem
Existing CXL HDM decoding techniques require a large number of physical decoders, leading to high costs, complexity, area consumption, and unnecessary power consumption, while many decoders incur misses and inefficiencies.
Innovation Solution
Implementing a prediction-based sequence for virtual HDM decoders, using a small number of physical decoders to efficiently translate host physical addresses to device physical addresses by predicting the most likely decoder based on temporal and spatial locality, reducing the number of physical decoders and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of physical decoders are used to handle CXL HDM decoding, then decoding coverage and reliability are improved, but hardware area consumption and power usage increase significantly
Solution Approach 1:
A single physical decoder is configured to perform multiple virtual decoder functions by dynamically loading different decoder configurations. The decoder can be reprogrammed to handle different HDM regions and address translations, allowing one physical decoder to replace many dedicated physical decoders, thereby reducing hardware area while maintaining decoding coverage.
Solution Approach 2:
The system uses dynamic configuration loading where decoder parameters and translation rules are loaded into a buffer memory and applied to the physical decoder at runtime. This allows the decoder to adapt its behavior based on the current HDM region being accessed, enabling a single physical decoder to dynamically serve multiple virtual decoder roles.
2Productivity
If a large number of physical decoders are deployed, then decoding capacity is improved, but power consumption increases due to many decoders incurring misses and operating unnecessarily
Solution Approach 1:
The system pre-loads decoder configurations and translation rules into a buffer memory before they are needed. When a memory access request arrives, the appropriate configuration is already prepared and can be quickly applied to the physical decoder, reducing the time the decoder needs to operate and minimizing unnecessary power consumption from decoder misses.
Solution Approach 2:
By using a single physical decoder that can be dynamically reconfigured to perform multiple virtual decoder functions, the system eliminates the need for multiple always-on physical decoders. This reduces power consumption because only one decoder is actively operating at any given time, rather than many decoders consuming power even when not fully utilized.
3Reliability
If multiple physical decoders are used to cover all HDM regions, then address translation reliability is improved, but device complexity and cost increase
Solution Approach 1:
The system introduces a buffer memory as an intermediary between the HDM regions and the physical decoder. This buffer stores decoder configurations and translation rules, allowing the single physical decoder to efficiently access and apply the appropriate translation parameters. This intermediary structure simplifies the overall system by eliminating the need for multiple parallel decoders while maintaining translation reliability.
Solution Approach 2:
The physical decoder is designed as a universal component that can be configured to handle different HDM regions and address translation scenarios. By making the decoder multi-functional through dynamic reconfiguration, the system reduces device complexity and cost compared to having multiple specialized decoders, while maintaining the reliability needed for accurate address translation.
Data Source
AI summary
A total number V of virtual host-managed device memory (HDM) decoder configurations are generated for the same total number V of HDM memory regions attached to a non-host computing device. Each virtual HDM decoder configuration in the virtual HDM decoder configurations corresponds to a respective HDM memory region in the HDM memory regions. A proper subset of one or more virtual HDM decoder configurations is selected from among the virtual HDM decoder configurations to configure one or more physical HDM decoders of a total number P of the non-host computing device into one or more virtual HDM decoders. The one or more physical HDM decoders configured as one or more virtual HDM decoders are applied to translate a host physical address (HPA) received from a host computing device in a memory access transaction involving the host computing device and the non-host computing device.