Link Interface Data Indicator Symbols Bandwidth Efficiency
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Solution Overview
Problem
The 8B/10B encoding technique used in PCI Express (PCIe) results in a substantial decrease in effective available bandwidth due to the use of two extra bits to convey data, leading to inefficiencies in bandwidth and power consumption.
Innovation Solution
A link interface technique that includes data indicator symbols to differentiate between data and special characters, allowing 8 bits of data to be represented with 8 bits instead of 10, thereby increasing bandwidth efficiency and reducing power consumption by ensuring that data is not misinterpreted as control characters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If 8B/10B encoding is used to avoid conflict between data and control characters, then reliability is improved, but bandwidth efficiency deteriorates due to using two extra bits
Solution Approach 1:
The patent extracts the conflict resolution mechanism from the encoding scheme itself and separates it into a distinct indicator symbol system. Instead of reserving entire code patterns for control characters, the invention uses a separate indicator symbol to mark when data matches a control character pattern, allowing the same code space to be used for both data and control without ambiguity.
Solution Approach 2:
The patent introduces an intermediary indicator symbol that mediates between data and control character interpretation. This indicator symbol acts as a flag that tells the receiver whether to interpret the following symbols as data or as a control character sequence, resolving the conflict without requiring separate code spaces.
2Reliability
If 8B/10B encoding is used to ensure DC balance and clock recovery, then signal integrity is improved, but power consumption increases due to higher bit rate
Solution Approach 1:
The patent changes the encoding parameter from 10-bit symbols to 8-bit symbols, reducing the bit rate by 20%. This parameter change maintains signal integrity through the use of indicator symbols and scrambling, while directly reducing power consumption proportional to the lower transmission rate.
3Ease of operation
If special symbols are used to indicate control characters, then ease of operation is improved, but device complexity increases due to encoding overhead
Solution Approach 1:
The patent extracts the control character indication function from the data payload and implements it through a separate indicator symbol mechanism. This separation simplifies the encoding logic by removing the need for complex code space reservations and conflict detection algorithms present in traditional 8B/10B encoding.
Data Source
AI summary
In some embodiments, a chip includes transmitters and generation circuitry to provide data symbols and special characters to the transmitters to be transmitted. The chip also includes match detection circuitry to detect when the data symbols match the special characters; and indicator symbol generation circuitry to create data indicator symbols in response to detected matches and to provide the data indicator symbols to the generation circuitry to be provided to the transmitters to be transmitted. Other embodiments are described.