of interest, i recently stumbled upon this on an x86 machine:
i dug into it some, and its part of the common phy framework within linux
with the right support code in the pi's ethernet driver, it could also do the same thing, in the event of a "damaged" cable (or one that never had the other 2 pairs)
Code:
[ 114.326838] Generic FE-GE Realtek PHY r8169-0-400:00: Downshift occurred from negotiated speed 1Gbps to actual speed 100Mbps, check cabling![ 114.326864] r8169 0000:04:00.0 eth0: Link is Up - 100Mbps/Full (downshifted) - flow control rx/txwith the right support code in the pi's ethernet driver, it could also do the same thing, in the event of a "damaged" cable (or one that never had the other 2 pairs)
Statistics: Posted by cleverca22 — Thu Sep 25, 2025 2:33 am