Slow wifi but ONLY on Windows PC's

[Koshka]

Here's a good question about a recent wifi problem we were having:  Background = We have about a dozen devices (windows computers, ipads, imac, smart TV's, and smartphones) connected to our home wifi network.  We have fiber optic in our neighborhood so our speeds are usually 90+ mbps.  A week ago, ALL 3 of our windows computers could not get a decent internet connection.  Sometimes the router's wifi name wouldn't even appear in the list of available networks.  If we could connect, it often took 10 minutes to load a page.  Again, this was happening ONLY on the 3  windows PC's. 

Here's the wild part:  The Imac, the ipads, the smart TV's and the smartphones all still had screaming fast internet speeds over the wifi.  It was ONLY the windows computers that couldn't get online.  They were all definitely connected to the same wifi network.  No question about it.

So...I rebooted the router, did a hard reset on the router, on the windows PC's I rebooted them, did a system restore on one of them, uninstalled and reinstalled the wifi adapters on all 3 of them... nothing made any difference.  Classic signs of a bad wifi signal right?

And before you suggest that perhaps a Windows update (or some other change to the Windows PC's) might be the culprit, know this:  2 of the 3 windows PC's I was using had been sitting in my closet for 6-8 months - not being used at all.  I only pulled them out so I could test my hypothesis (that my windows PC wasn't the problem).  So it couldn't possibly be any sort of recent update or other change that caused the problem, since those 2 computers hadn’t been connected to the internet for many months.

Logically, if multiple computers are having the same problem getting a good wifi signal, then the problem has to be either the router, or the internet signal coming into the house.  It can't be the fault of the computers if it's happening to 3 different ones.  But then why did ALL of the other devices continue to operate normally?

The AT&T tech was just here, he swapped out the router, and now everything is great.  But I can't stop wondering how in the world this could have happened. 

Any ideas or suggestions would be much appreciated.  Thanks.

[DaveLembke]

The AT&T tech was just here, he swapped out the router, and now everything is great.  But I can't stop wondering how in the world this could have happened.

Router was likely dual band G/N so 2.4Ghz and 5Ghz and so say the 2.4ghz was not healthy and that is what the Windows machines were using and all other devices were on the 5Ghz band this would perform exactly as you experienced with router fixing the problem.

[Koshka]

Thank you.  Makes sense.

It was a dual band router.  But the only time I was given the option (to choose either 2.4 or 5 ghz) was when I was using the wifi extender.  The extender broadcasted both bands, but I'm pretty sure the router itself only broadcasted the main band (the wifi name without any "2.4" or "5" after it).  All of the devices were originally connected to the main router.

So...I have a few follow up questions, if I may:

1.  Is there a way to tell which band a particular device is connected to?

2.  Is there a way to choose a particular band when connecting a device to wifi? 

2.  Why did all of the windows computers automatically choose one band and all of the other device automatically choose the other?

Thanks in advance.