Problem with 52PI EP-0146 Network Interface (Raspberry Pi Router Board for CM4 module, SKU 103110042)

Hi, I’ve received this board and have noticed a strange problem - the CM4 ethernet port (Port0) works fine and achieves full gigabit performance sending and receiving, however the additional ethernet port provided by the rtl8111 on the router board (Port1) only achieves about 80mbit/s sending, though receive is full gigabit. (Tested with iperf3, using the same patch lead and switch port each time, with iperf3 -s running on my current Intel J1900-based router)

This isn’t link negotiation, 1000baseT-FD is negotiated on both ports and there’s no packet errors being logged.

The weird bit though - if I blow on the chip to rapidly cool it, the send performance increases to about 300~400mbit/s.

I decided to try this after seeing Jeff Geerling’s video review of this board where he noted that it would slow down when it heats up.

Thing is though the chip isn’t hot yet! If I put my finger on it, it’s a little warm but way cooler than other chips on the board. The issue with heat v performance that he describes seems to be far less severe than what I’m noticing on this unit.

I suspect I have a defective rtl8111E