Scaled PCI Express Credits Prevent Link Stalling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing PCI Express platforms face limitations in transmission bandwidth as the existing flow control mechanisms cannot convey enough credits to cover the round trip time of the Link, leading to 'stalling' of PCI Express Links, especially as transmission bandwidth increases.
Innovation Solution
The introduction of Scaled Flow Control Packets (SFCPs) that include a scaling factor for flow control credits, allowing for greater credit values while maintaining compatibility with existing PCI Express formats, and a Flow Control Credit Controller to manage and negotiate these scaled credits between PCI Express components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If existing flow control mechanisms are used, then compatibility with existing PCI Express formats is maintained, but transmission bandwidth is limited and Link stalling occurs
Solution Approach 1:
The patent applies parameter changes by introducing a scaling factor that multiplies the flow control credit values. Instead of changing the fundamental credit-based flow control mechanism, it scales the credit parameters to larger values to accommodate increased transmission bandwidth requirements while maintaining the same protocol structure.
Solution Approach 2:
The patent adds a new dimension to the flow control packets by including a scaling factor field alongside the existing credit value fields. This additional dimension allows the system to convey larger effective credit values without fundamentally altering the packet structure or breaking compatibility with existing formats.
2Reliability
If flow control credits are increased to prevent stalling, then transmission bandwidth increases, but existing PCI Express packet formats cannot accommodate the larger credit values
Solution Approach 1:
The patent embeds the scaling factor information within the existing flow control packet structure, nesting the new functionality inside the conventional packet format. The scaling factor is included as an additional field that works in conjunction with existing credit value fields, allowing larger effective credit representation without replacing the entire packet structure.
Solution Approach 2:
The scaling factor acts as an intermediary that translates between the limited credit value fields in existing packet formats and the larger credit values needed for high-bandwidth operation. This intermediary element enables the system to overcome the format limitations while maintaining compatibility with existing packet structures.
3Productivity
If scaled flow control packets are implemented, then Link saturation and efficient communication are achieved, but compatibility with non-scaled PCI Express Ports must be maintained
Solution Approach 1:
The patent implements dynamic negotiation where the scaling factor is not fixed but is instead negotiated between communicating endpoints. The system can adaptively determine whether to use scaled or unscaled credit values based on the capabilities of the communicating parties, allowing flexible operation across different device types.
Solution Approach 2:
The flow control packet structure is designed to be universal by incorporating the scaling factor in a way that allows the same packet format to serve both scaled and unscaled operations. Endpoints that support scaling can utilize the enhanced credit values, while those that don't can ignore the scaling factor field, making the system universally compatible.
Data Source
AI summary
The disclosure provides a PCI Express Scaled Port, a computing device and a method of communicating between PCI Express components. In one embodiment, the PCI Express Scaled Port includes: (1) an interface configured to communicate flow control negotiating packets with another PCI Express Port and (2) a FCC Controller configured to generate the flow control negotiating packets, wherein the flow control negotiating packets include a flow control credit for PCI Express packets and a scaling factor for the flow control credit.