UGHH!! I can't believe it was this simple....
I have been dealing with crappy download speeds for ages on my main desktop, despite having a 500mbit connection. I had always chalked it up to some services\sites throttling my download speeds until recently when my daughter was able to download a Steam game on her laptop (wifi) in a fraction of the time it took me to download it on my desktop. I had assumed this was a Steam issue, because I have noticed this with Steam for a very very long time. I did a complete 100% reinstall of Steam and for whatever reason it seemed like it fixed it when I tested it immediately after that.
However, since then I have tried downloading some other things from Steam and noticed it was back to the crappy speeds (2-5MBytes\sec on a 500Mbit connection... should be 50-60MBytes+). I have tried several things and nothing seemed to fix it. Oddly enough, doing normal internet speed tests always reported that I was getting 500mbit download, so I just continued to assume it was a Steam issue.
Tonight though, it was especially bad. I was attempting to play a game online that frequently requires workshop levels to be downloaded as you join. I was consistently the LAST PERSON to download the level, oftentimes getting booted from the server long before the download would finish.
I don't even know how I got there now, but I stumbled upon this page that is intended to test bufferbloat (which I actually don't have issues with). The discussion I found that link in had an interesting reply that said "Hey! That test gives exactly the same result as my slow Steam download speed!" ... so I figured it'd be worth testing. Sure enough: THAT test showed I was only hitting a max of 120mbit\sec... usually barely breaking 100.
So, I now knew it was NOT Steam.
I proceeded to try a USB 3.0 ethernet adapter, a different cable, connecting straight to the modem... all had exactly the same result. The kicker though is that connecting my daughter's laptop to the same ethernet connection resulted in a whopping 508mbit\sec in that same test!
Ugh! All this time, it has been an issue with something in Windows. Not hardware related, not network related, not ISP, not Steam.
This also explains some oddly slow network file transfers I've had lately too (I don't do this often so it slipped my mind). I had googled the slow network transfer issue a while ago and couldn't really figure it out. I even asked over at smallnetbuilder and didn't really have any solid leads.
Now, I'm amazed this worked because I wasted a bunch of time with Claude the last time, running in circles checking stuff that wasn't even applicable. This time, within 5 minutes I had it fixed.
I explained the situation very briefly, highlighting that it seemed to be an OS issue and not anything external to my PC. Then Claude told me it was probably some incorrect or corrupted settings related to the TCP/IP stack (which is not something I know anything about). It told me to input these at an elevated command prompt:
netsh winsock reset
netsh int ip reset
netsh int tcp set global autotuninglevel=normal
(all of these look familiar to me, but it's nothing I've messed with in years... clearly.)
I did that, rebooted and now I am getting 508mbit\sec in the same test. Ughhh... I am embarassed to admit I have been dealing with slow Steam downloads for years and I just rarely download anything large enough anywhere else to notice that it wasn't just Steam. I'd be furious if I wasn't so relieved to have fixed this.
Finally. 😑
Now for some blitting from the back buffer.