2 PCs, one slowing down internet of other !

  1. Posts : 45
    Windows 10

    2 PCs, one slowing down internet of other !

    This is ultra strange. I have 2 PCs. For the last 3 months I have been having issues where just one of the PCs internet would slow down from the usual 60mbps to 20mbps or less (only on single thread, multi-thread was fine). Normally the first 2 minutes of the computer being turned on the speed would be fine, then it would slow right down. For months I tried to diagnose the problem, I tried 3 different USB3 to Ethernet adapters just in case my NIC was at fault. I bought another NIC card just in case. I turned off various services and uninstalled software. I changed ports on my gigabit switch, I tried direct connected to router, I tried a new 5e cable, cat6 cable, etc. Then when my slowed PC broke the other day I got a new PC (except for the hard drives and PSU and USB3 card and graphics) and was slightly relieved I had an excuse to finally end this problem as I assumed my motherboard was causing it, and yet the problem STILL exists, even with a fresh Windows 10 installation on a new PC (motherboard, CPU and memory was new).

    So one thing I never tried was turning the other PC off that is connected to the network, it runs 24/7. I didn't turn it off before to test because the speed was perfect on that computer, always a rock solid 60mbps. So I ignored it thinking that can't be the cause. Then today when I was at my wits end, given the new PC has the same issue, I decided to turn off the other PC. Then I found the speed was finally normal, talk about a massive face palm. But what the hell does this mean ? Why is a PC that shows a rock solid 60mbps (which is the max speed of my internet) in both single and multi-thread the likely cause of the internet speed on my other PC being slowed down in single thread ?

    Is there any logical possible cause ? Some kind of loopback issue ? Both have the same hotmail username. Both sync OneDrive and settings. Both are Windows 10 Pro. Both are Ryzens (although my last PC was an i7 and the same happened with that).

    One thing to note, if I manually disable and then re-enable the network adaptor on the slowed down PC then I get full speed for approx 1 minute before it slows again.
      My Computer

  2. Posts : 1,300

    1. Can you describe your network topology?
    2. Can you describe the means you use to measure network speed?
      My Computer

  3. Samuria's Avatar
    Posts : 6,106
    windows 10

    If you get 60 meg with two PC's then it could give 30 meg each but a PC starts a download and grabs 50 meg speed the other will only get 10 so it's a case of what the good PC is doing it may be downloading updates taking all the bandwidth. If the bad PC gets full speed when only it's on then it's not faulty
      My Computer


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