Aggregated Credit Return for Multi-Link Data Flow Control
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Solution Overview
Problem
High-performance computing applications require significant processing power and efficient data communication between dice, which consumes substantial power, especially in die-to-die communication within IC packages, necessitating improved technologies for digital data communication.
Innovation Solution
Implement credit-based flow control using a common reverse channel for multiple data links, coupled with clock-forwarded data link signaling, source-side clock calibration, and clock forwarding between deserializer and FIFO to achieve zero-cycle or near-zero-cycle data transfer, and phase alignment of data lanes to optimize power efficiency and data transfer rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If credit reporting logic is implemented for each data link, then flow control accuracy is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple individual credit reporting logic units into a single aggregated credit reporting unit. This unit receives credit status information from multiple data links, aggregates it, and generates a unified credit report. This merging approach maintains flow control accuracy across all data links while reducing the overall device complexity by eliminating redundant reporting logic in each individual link.
2Reliability
If multiple separate reverse channels are used for credit reporting, then reporting reliability is improved, but power consumption increases
Solution Approach 1:
The patent merges multiple separate reverse channels into a single shared reverse channel for credit reporting. The aggregated credit reporting unit consolidates credit status information from multiple data links and transmits it through this single channel. This approach maintains reporting reliability by ensuring all credit information is transmitted while significantly reducing power consumption by eliminating redundant channel operations.
Solution Approach 2:
The single reverse channel is designed to serve multiple data links simultaneously, making it a universal communication path. The aggregated credit reporting unit multiplexes credit information from different data links onto this shared channel, allowing the channel to perform multiple functions and serve multiple purposes, thereby reducing overall system power consumption.
3Device complexity
If data delivery and data extraction are synchronized, then buffer management is simplified, but data transfer flexibility is reduced
Solution Approach 1:
The patent implements a feedback mechanism through credit reporting that allows the system to handle asynchronous buffer operations while maintaining effective control. The credit reporting logic continuously monitors buffer occupancy and provides feedback about available buffer space to the data source. This feedback enables the system to tolerate asynchronous delivery and extraction operations without requiring complex synchronization, thus simplifying buffer management while preserving data transfer flexibility.
Data Source
AI summary
Systems and methods are disclosed for credit-based flow control of multiple data links using a common reverse channel. The links transfer data from a source to respective buffers at a sink. Credits represent available buffer space. For each data link, a credit counter at the source is decremented as data is transmitted and incremented as the sink returns credits. Reporting logic at the data sink generates a credit report as sink logic retrieves data from the buffer, freeing buffer space. Encoding logic aggregates the credit reports from multiple links for transmission over the common reverse channel to the source, where individual credit reports are extracted and distributed among the links, for update to the respective credit counters. For each link, data transmission pauses when the credit counter decreases to a threshold. Return multiple links' credits over a single reverse channel saves power. Variations are disclosed.