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Two Out Of Three PCs Have Slow Download But Fast Upload

Two Out Of Three PCs Have Slow Download But Fast Upload

Contributor mechanikism
Posts: 4
Registered: ‎10-02-2018
Message 1 of 7

I've had FiOS Gigabit for about a year and a half, and it was pretty solid up until recently. I had verified speeds when we first got the service by using several third party sites (primarily speedtest.net), which clocked them at 800+Mbps so all seemed well. Two weeks ago, my desktop PC started having all kinds of connectivity issues, including terribly laggy and inconsistent download speeds, laggy gaming performance, and even a complete loss of connectivity for a few minutes one night. I've been looking into it, and what I've found makes absolutely no sense to me.


I have three PCs on my home network, all of which were getting gigabit speeds until this started. On two of these PCs now, speed tests show download speeds between 300 and 600Mbps, usually in the mid 400s on one and 600s on the other. Strangely, upload speed from these two PCs is perfect, clocking over 900. On top of that, the third PC on my home network shows perfect download and upload speeds, 900+ on each. If I take the same exact patch cable on the same router port from the fast PC to the other PCs, they still report half download speeds.


I've run Verizon's speed test on all three, and here's where it really loses me: all three report 900+ for both upload and download. If that tool is accurate, what this means is that for two of my PCs, connectivity through to Verizon's network is fine, but drop to half speed going beyond that - but the third PC does not have this problem, and gets fast speed all the way through.


I spent an hour on the phone with a Verizon rep who went through factory resetting the router with me, which had no effect on anything (I've been using basically the default settings all this time anyway). They also restarted the ONT box. A tech came out to my house today and didn't have much input beyond connecting his tablet to my router and showing that Verizon's speed test was clocking his device at 900+. I showed him the speed tests from all three PCs, and he said it must be something specific to the two PCs.


I've combed through every setting. I've reinstalled the NICs, disabled and re-enabled all offloading and other features. Nothing has made any difference. All are directly connected to the router, and if I switch connections between the working and nonworking ones, there's no change. Again, if Verizon's speed test is to be believed, then all three of these PCs have perfect connectivity to their network, but only one is allowed to have fast speeds beyond it for some reason.

Posts: 1,148
Registered: ‎06-24-2018
Message 2 of 7

If one of your devices and the tech’s tablet is handling it then you are getting good speeds. 

Besides nic cards. The pc’s processor, firewalls, virus protection are all factors. Definitely sounds like issues with your equipment. 

Bronze Contributor II
Bronze Contributor II
Posts: 75
Registered: ‎12-28-2011
Message 3 of 7

Hey mechanikism - This has been happening on my Win 7 Pro 64-bit PC with 1Gbps FIOS for some time, but the #1 reason is Avast Free AV.  It slows download speeds to 450 Mbps ±, but uplaod is fine at or better than 800 Mbps.

The Verizon speed test says the same thing - high speed from them to ONT (or G1100 Quantum router?) and an issue from ONT (or router?) on.

And if I temporarily disable the Avast "shields", my download goes up to 800 Mbps.

PLEASE TRY  a similar test and let us know.

Contributor mechanikism
Posts: 4
Registered: ‎10-02-2018
Message 4 of 7

I ended up discovering that the browser I was using is impacting the tests. The two slow PCs were being tested in Chrome, while the fast PC was using Firefox. If I run the test in Chrome on the 'fast' PC, it gets significantly lower speeds. If I run the test in Firefox incognito mode on my PC, it gets much better speeds (but they're not always consistent, like they are on the 'fast' PC).


I'm trying to figure out what the two 'slow' PCs have in common that the 'fast' PC doesn't have. So far, I'm coming up empty.

Contributor mechanikism
Posts: 4
Registered: ‎10-02-2018
Message 5 of 7

Also, just to note, I have no anti-virus or anti-malware outside of Windows Defender currently installed. I've tried temporarily disabling Defender, and that didn't help.


I did have Malwarebytes installed last month for a system scan (came back negative), but have since uninstalled it.

Platinum Contributor III Platinum Contributor III
Platinum Contributor III
Posts: 7,649
Registered: ‎11-04-2008
Message 6 of 7

Check the network card in the "slow" pcs.

Make sure they have speed at least as good as fast PC.
Also check to see if there are driver updates for them.

If a forum member gives an answer you like, give them the Kudos they deserve. If a member gives you the answer to your question, mark the answer as Accepted Solution so others can see the solution to the problem.
Contributor mechanikism
Posts: 4
Registered: ‎10-02-2018
Message 7 of 7

Both NICs in the 'slow' PCs are showing 1Gbps speed on their connections statuses. They can hit between 800 and 900Mbps on speedtest.net if I'm using Firefox and not Chrome or Edge as the browser. I went through and updated drivers, and did a full reinstall of the adapters on both (I actually used Windows 10's networking reset option on one, and just did a normal uninstall via Device Manager on the other). 


It might sound silly at this point to chase the issue if it's only affecting certian browsers, but my concern is that whatever the issue is might be throttling other protocols or applications on these PCs without me really having a way of knowing.

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