PCIe Root Complex VSEC Pin Reduction
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Solution Overview
Problem
In PCIe systems, the increasing integration of the Root Complex with CPU cores to form System on Chip (SoC) leads to valuable pin usage constraints, making it costly and inefficient to rely on external pins for initializing and configuring registers, especially for hot-plug operations.
Innovation Solution
The implementation of a Vendor Specific Enhanced Capability Structure (VSEC) within the Root Complex, which allows programming of Slot Capabilities and Status Registers without external non-volatile memory, combined with shadow registers on a less expensive chip like a Slot Interface Chip (SIC), reduces the number of external pins required and enables transparent communication of register changes through privileged software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If external pins are used to initialize and configure registers in PCIe systems, then register initialization and configuration is achieved, but pin count and system cost increase
Solution Approach 1:
The patent extracts the register initialization function from external pins and relocates it to internal resources. Specifically, it uses the Vendor Specific Enhanced Capability Structure (VSEC) within the Root Complex to store platform-specific initialization values, eliminating the need for external pins to provide these values. This extraction resolves the contradiction by removing the pin dependency while preserving the initialization functionality.
Solution Approach 2:
The VSEC acts as an intermediary structure between the Root Complex and the initialization requirements. Instead of directly using external pins to configure registers, the system uses the VSEC as a mediator that stores initialization values and makes them available through the configuration space. This intermediary approach eliminates pin dependencies while maintaining the necessary configuration capabilities.
2Adaptability or versatility
If external pins and serial EEPROM are used for hot-plug operations, then hot-plug functionality is achieved, but system cost and complexity increase
Solution Approach 1:
The patent extracts hot-plug operation functionality from external pins and EEPROM, relocating it entirely within the Root Complex. The VSEC stores hot-plug configuration values and status information internally, eliminating the need for external pins and serial EEPROM. This extraction reduces system complexity while preserving hot-plug adaptability.
Solution Approach 2:
The Root Complex with VSEC performs self-service by internally storing and managing hot-plug configuration data. Instead of relying on external components for hot-plug operations, the system uses its own internal resources (VSEC in configuration space) to provide these functions, thereby reducing overall system complexity while maintaining versatility.
3Productivity
If Root Complex is integrated onto the same die as CPU core to form SoC, then integration and performance are improved, but pin availability becomes constrained
Solution Approach 1:
The patent extracts the initialization and configuration functions from external pins and relocates them to internal VSEC structures within the Root Complex. This allows the Root Complex to be fully integrated onto the same die as the CPU core without requiring additional external pins for initialization purposes, thereby resolving the pin availability constraint while maintaining high integration levels.
Solution Approach 2:
The VSEC serves multiple functions: it stores platform-specific initialization values, maintains hot-plug configuration data, and provides status information. This multi-functionality allows the Root Complex to perform various tasks using its internal resources rather than requiring separate external pins for each function, thus resolving the pin constraint in highly integrated SoC designs.
Data Source
AI summary
A method and system to facilitate Peripheral Component Interconnect Express (PCIe). The PCIe may be facilitated in such as way as to limit pins consumed by a Root Complex, switch, or other chipset included on the same die a central processing unit (CPU). A slot interface card (SIC) or other devices having less expensive pins may be used to connect to and communicate with the slot.