Gigabit Network Card is only showing 100mbps in network adapter>status

I'm using 3600+B450 tomahawk max mobo with CAT6 LAN cable plugged in. I'm using Win10 1909 18363.815

All the while it has been 1Gbps until few days ago it keeps disconnecting and reconnecting by its own. And when reconnects it shows 100mbps.

Cable should be working fine as i plugged into my laptop and it shows 1gbps. Could it still be my cable issue?

Things I've done:

bought new router

changed duplex to 1gbps

updated bios

reinstall network adaptor to newest update

Caledon Ken said:

Hi wintermilk. Welcome to TenForums @wintermilk


If you click on Power Management tab in device properties have you tried disabling "Allow the computer to turn off to save power"?


If once it goes to 100Mbps if you run the network trouble shooter will it reset itself to 1000Mbps?


If you enter this command

ipconfig /all

and look at your wired NIC how long is the lease being assigned, days or hours?

Is your router firmware up to date?

Hi, thanks for your reply..

I'm using AMD Ryzen High power Plan, which disables all related sleep activities

If i run the trouble shooter, it will say it cannot find any problem


My wired NIC lease is being assigned for 24hours.

Yes router firmware is up to date

swarfega said:

You need to make sure that all the things between you and your router are able to achieve gig speeds. So the nic card, the ethernet cable (try cat 6 if your on cat 5), and your router ports (check the router's manual).

Thanks for the reply. Initially i had gig speed with this pc until this 100mbps prob appeared. Currently my other laptop is receiving gig speed with the same cable.

Another pointer to add on.
Sometimes when i change the port on the router, the pc reads 1gbps. After 1-2 hrs it will disconnect and reconnect back to 100mbps

swarfega said:

Have you been into the card's properties. You usually can set the speed there.

Are you referring to the duplex? I have already tried both 1gbps full duplex and auto nego

swarfega said:

Yea I was.

Have you tried the card in different ports?
Also ethernet cables can fail so do you have another one to test with?

I have tried plugging the cable into another port of the router. Initially it will read 1gbps, after awhile, it will disconnect and reconnect back to 100mbps. I have tried with 5e, same issue