I have built a modest home server from old parts. Motherboard is a Foxconn A6VMX with onboard 100Mb LAN. But I'm not using that port, I use a Gigabit PCI (not PCIe) card, which is working well under Ubuntu Server 22.04, to connect to my Gigabit switch.
Since the server runs 24/7, I've been trying to reduce idle power consumption (measured at the wall socket with one of those plug-in power meters). I have it down to around 42~43W, so not too bad, but shaving off a few more Watts would be even better.
Browsing the BIOS configuration pages, I realised I had not disabled the onboard 100Mb LAN. I did that, and the idle power consumption dropped to 35~36W, which quite surprised me, I was only hoping/expecting to save a couple of Watts.
But I then realised the server was not connecting to the router and had no IP address. The LEDs on the Gigabit card seemed to be flashing merrily away as usual.
So I've re-enabled the onboard LAN and the server is connecting ok again.
I would like to try again for that 7~8W saving, but don't know how to get the server to connect. I don't understand why disabling the onboard LAN would affect the PCI Gigabit LAN at all.
Google and the forum search don't seem to find me any similar topics, perhaps I'm not using the best search terms.
Can anyone help me to diagnose what's going on here? Please let me know what relavant details I need to provide.
Thanks!
Paul