08-24-2016, 09:51 AM
Just an update to this issue, I seemed to narrow it down to a single board that was giving me ~480Mbps transmitting to any of the other boards, while making a faint 'chirp' noise, but could receive at ~850Mbps and make no noise.
I tried the same cable reversed, different cable and different switch port and ruled them out as causes.
I *think* it might be very slightly dodgy wiring in the Ethernet socket on that board? Plugging/unplugging a cable sometimes works consistently at full speed (in either direction) without any EMI noise, and other times is slow and makes a noise. I can't reproduce it plugging/unplugging a cable into one of my other boards.
I tried the same cable reversed, different cable and different switch port and ruled them out as causes.
I *think* it might be very slightly dodgy wiring in the Ethernet socket on that board? Plugging/unplugging a cable sometimes works consistently at full speed (in either direction) without any EMI noise, and other times is slow and makes a noise. I can't reproduce it plugging/unplugging a cable into one of my other boards.