Why Do My Download Speeds Vary so Much Between Computers?

In an ideal world, you would pay for super-fast internet service, plug your cable modem into a fast enough router, and get blazing download speeds for every device in your home. Unfortunately, we live in the real world, which often paints a very different picture.

In the real world, you pay extra for an “unlimited” internet service with a data limit and end up renting a cable modem from your ISP for even more money. It’s a router / modem hybrid that gives you mediocre connectivity for a lot of your devices all over … well, part of your home. You ponder what you need to do to get a wireless connection to cover the dead spots and end up buying a crappy extender that helps you achieve a fraction of the speeds you pay for. You wonder why it is so difficult.

Lifehacker reader John may not be quite as bad in the setup as it is, but his question this week Tech 911 Q&A reminds me that we live in a world in which the average person has to jump through hell a lot of hoops (maybe) set up a quick Internet connection. He’s writing:

I have 2 computers connected to the same new Netgear managed switch. All my equipment is capable of 1000 Gbps. As an example, here are two screenshots of the speed tests I ran on both PCs: first PC1 and then PC2.

I don’t understand the huge difference in speed between testing on the same subnet through the same router / cable modem?

PC baud rate # 1:

PC baud rate # 2:

Troubleshooting inefficient networks can be a PITA

John actually sent me a lot more details about the various things he already learned to maximize the connection speed on his 1Gbps plan. (That’s a lot! Two cable modems, two mesh systems, lots of Ethernet and coaxial cable. Lightning strike . This is a true story.) However, for brevity, this is its root problem: inconsistent performance, even over a wired connection.

At least I assume wired. Let’s deal with this first: if PC # 1 is connected via Ethernet and PC # 2 is connected via a wireless card, this is your problem. It is much more difficult to get a consistent and blazingly fast signal over Wi-Fi – there are many things that can affect the quality of your connection and the resulting speed , which I have written about in numerous columns.

It’s also possible that the speed test reports different results simply because … they do it . However, strange to see such dramatically different results of the same test speed when accessing the same theoretical place of testing. I am assuming that you have run the test quite a few times and have consistently seen large performance differences between your two PCs.

The first thing I can do is try some more speed tests in case there are any abnormalities with the Speedtest . I’ve always enjoyed using fast.com , but there are others . You want to determine if you observe the same crazy difference between your two systems in multiple tests. If so, we can begin to narrow our troubleshooting down to something that is potentially related to a sick system. If not, or the results are reversed, then you probably want to take a step back and think about troubleshooting some common issues (or just dealing with the odd variances).

For the sake of argument, let’s say your various tests show that PC # 2 is still slower than PC # 1. There is a lot we can do to fix this, so let’s dig in right now.

Start by replacing the Ethernet cables used by the two computers, or plugging in with another new, cheap Cat 6 cable. There might be a problem with the network cable you’re using on your slower PC. It can also be rated too low for the distance you are using it (and the speed you hope to achieve). Perhaps you even have some kind of loose connection. Try a different cable. Run your tests. See what happens.

I am assuming PC # 1 and PC # 2 are connected to your router in the same way. If PC # 1 has a direct Ethernet connection, but PC # 2 is connected to a power line adapter, and this is how you can provide it with an Internet connection without running an Ethernet cable all over your home, this is likely the bottleneck. When you run your tests, make sure you are connecting directly from your router to your desktop.

Remember to reset all your network settings before running speed tests. Reboot your modem, router, PC, and any other devices in between – even turn off and on any switches you use as part of your network (what I had to do to get the speed of my desktop PC connected to ethernet back up again.) Yes, the switches are generally dumb, but sometimes they can work.

If that doesn’t fix the problem, dig deeper. Try connecting the Ethernet cable (s) to different ports on your switch or router. Does PC # 2 have a second Ethernet port that you can use? Try this and see what happens. In terms of hardware, I can’t think of anything else – unless you’re using some kind of discrete network card or USB adapter to connect to the Internet on PC # 2, which could also be your point of failure.

In terms of software, check to see if there are any firmware updates you can install on your modem, router, switches, or motherboard – just to name a few. There may be an update that fixes a defect that would otherwise slow your speed. It is also possible that one setting or another is faulty, and flashing the updated firmware (which usually returns your settings to factory defaults) may help fix this.

If not, consider resetting your modem to defaults, then your router, and then possibly even your BIOS and / or operating system. Yes, it’s a wipe-and-reinstall approach – an option I would recommend as a last resort, but it’s always on the table for you to try. (Are there any strange networking applications on your system that you don’t recognize or use? Removing them might help .)

Check if your PC (or network interface) manufacturers have provided any updated drivers that you can install. While I’m not sure what exactly is causing your second PC to slow down, it’s easy to fix. While you are doing this, update the DNS settings on PC # 2 to something faster (like Google DNS or Cloudflare ) instead of what you get from your ISP.

You can also try resetting your TCP / IP stack by opening a command prompt as administrator and entering the following :

netsh int ip reset

I would not advise buying something new until you have exhausted all possible troubleshooting options. If you have a friend with an Ethernet adapter that you can use, see if that improves your speed at all. A cheap PCI or USB port will do, although I always prefer the former as it offers less room for complications. (Luckily, if you need to buy one, a decent gigabit card can be purchased for under $ 20 – a small price to pay to double your internet speed.)

But that’s all I can think of. Hopefully one of these methods will solve your difficult problem. But even if they don’t, 400 Mbps on one system isn’t all that bad. I know this is not the 700+ Mbps you hoped for, but you only really notice the slowdown when uploading huge files. Otherwise, if there are any positives to be found in this problem, I would expect latency (and DNS) to affect your typical web browsing experience more than this speed difference.


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