Yes, I know they are entirely passive. That’s why the source and sink need to determine the maximum rate literally based on trial and error. The source tries

Yes, I know they are entirely passive. That’s why the source and sink need to determine the maximum rate literally based on trial and error. The source tries a link speed (and other parameters such as drive strength and pre-emphasis), the sink reports back home many symbol errors it detected. Rinse repeat until a stable configuration is found. For marginal connections that’s often not sufficient. After the introduction of DSC, DP has mandatory support for Reed-Solomon forward error correction, which is a great help in fixing occasional error burst. It can be enabled when DSC is off, but I don’t know that happens in practice.