Net Speed Cap Issues

[Cynaxia]

Hey, I've upgraded my PC a whiles back now, having issues with internet speed cap since the upgrade, related to motherboard I assume

Issue: sometimes my net speed on speedtest is 100mbit with task manager showing network usage being 100%, and sometimes when I restart my PC it goes all the way up to 500mbit with task manager showing network usage being 50% (500mbit being my max speed provided by my ISP)

To note: when I'm fixing this issue for time being with restarting PC, I'm literally just restarting PC, not touching BIOS settings or anything else.

This 100mbit cap comes and goes randomly, not sure what's causing it, tried different cables too, and I got 2 PCs sitting on the same network, only PC in question is affected, no matter the network load

Present motherboard: asrock b650 pg riptide (random caps happening on this one)

Previous motherboard: aorus x470 ultra gaming (never had any issues on this one)

 

Any help/suggestions on preventing this random internet speed cap from occurring are appreciated !

[StDragon]

Ethernet has 4 twisted pair, so 8 wires total. If one of the twisted pair is bad, your 1gig link will step down to 100mbit. Hence the limitation.

You can try swapping the patch cable, reconnect, or you might need a cable tester to validate full continuity with all 4 twisted pairs from end-to-end.

Sometimes it's not the patch cable, but the RJ45 jack in the wall. I've seen a wire come loose that needed to be re-terminated. Though be careful not to cut too much line as you might not have much cabling to work with. But again, use a cable tester to isolate the faulty segment. 

Edited November 16, 2023 by StDragon

[StDragon]

Also be sure to update the driver. There's been numerous bugs with those 2.5GB NICs. Your new MB has the Realtek RTL8125BG controller.

https://www.realtek.com/en/component/zoo/category/network-interface-controllers-10-100-1000m-gigabit-ethernet-pci-express-software

 

Note: with Windows 11, you'll want to be using the new NetAdapterCx instead of the older NDIS type.

[Cynaxia]

On 11/16/2023 at 3:01 AM, StDragon said:

Ethernet has 4 twisted pair, so 8 wires total. If one of the twisted pair is bad, your 1gig link will step down to 100mbit. Hence the limitation.

You can try swapping the patch cable, reconnect, or you might need a cable tester to validate full continuity with all 4 twisted pairs from end-to-end.

Sometimes it's not the patch cable, but the RJ45 jack in the wall. I've seen a wire come loose that needed to be re-terminated. Though be careful not to cut too much line as you might not have much cabling to work with. But again, use a cable tester to isolate the faulty segment. 

Not a mechanical issue, tested other cables on this PC and this cable on other PC only PC in question keep getting affected

[Cynaxia]

On 11/16/2023 at 3:14 AM, StDragon said:

Also be sure to update the driver. There's been numerous bugs with those 2.5GB NICs. Your new MB has the Realtek RTL8125BG controller.

https://www.realtek.com/en/component/zoo/category/network-interface-controllers-10-100-1000m-gigabit-ethernet-pci-express-software

 

Note: with Windows 11, you'll want to be using the new NetAdapterCx instead of the older NDIS type.

I'm gonna try updating , but no high hopes, I did update drivers a little while back didn't help

Issue is always the same, I sit on 500mbit speed till a random 1 second disconnect happens, only noticable when you play a game for example, because you get kicked out, and then next second I'm capped at 100mbit, restart always helps to go back to 500mbit

[StDragon]

1 hour ago, Cynaxia said:

...because you get kicked out, and then next second I'm capped at 100mbit, restart always helps to go back to 500mbit

That's a classic case of the NIC dropping the 1gig link and renegotiating to 100mbit.

Check your Windows Event logs to see if there's any corroborating evidence of this.
https://answers.microsoft.com/en-us/windows/forum/all/network-connection-event-logs/517b72ce-240b-4f86-a560-e11a86ed03be

From what I've read about the Realtek 2.5G NICs, the low power mode is buggy, so that might be the culprit. I would go for the "Not Support Power Saving" version of the driver. It's been reported that power saving modes is about 2 watts. It's not insignificant for a controller chip, but in the grand scheme of things, probably not worth caring for that extra power efficiency if it's killing your connection in the process.