How to determine a computer's max connection speed?

I’m trying to determine the maximum data connection speeds of our computers and network. I hope that is worded correctly.

We have Comcast internet with a published 500Mbps service. Out of the Comcast router, our feed goes to an Araknis router, then a switch, and then via ethernet to the computers plus to Ruckus APs for Wifi. I think this old beginner has that described correctly.

I thought we were falling way short of the published service speed since my iMac was showing a little less than 100 Mbps whether using Ethernet or Wifi. Measured speed by Ookla and Comcast speed tests.

But then I checked my wife’s computer on both Ethernet and Wifi. Both were around 550 Mbps on her 2018 iMac. So that would say Comcast is delivery the published speed.

I then tried my 2019 MacBook Air travel computer. It is showing speeds around 135 Mbps over Wifi.

And then my computer which is a 2015 iMac brings up the rear at 90 Mbps on both Ethernet and Wifi.

I now suspect that either each computer has a maximum connection speed or we are losing speed through the network. But I have no clue where to start to educate myself. I assume I should have found a good site with a search but I failed.

Any education or site references will be very much appreciated.

Thank you.

I don’t think the “perceived” bandwidth on the mac is actual. I too, have a mac (mac mini 2012) that shows no more than 404Mb/s (remember that is bits, not bytes) which is about 50MBytes/sec. Yet, I have 1Gb/s service from Fios. Now on my PC (windows 10, connected same via enet (cat5e/cat6) to gig SMC switch to Orbi router) states I have 963Mb/s down and 909Mb/s up. +/- 5% if I run tests several times (factor in home load, IoT devices, traffic). So, I believe that Apple’s networking is doing a speed that it doesn’t actually indicate correctly. Just like the ridiculous “dumbing down” of the installer times “about 2 minutes” then it increases 2 minutes later to “about 10 minutes”.
Either there are discrepancies with the controllers per generation of macs, the OS has overhead it isn’t factoring in, or we aren’t getting advertised bandwidth of 100/1000Mb/s Apple devices (just like a 27" CRT Television is really 25.9" diagonal) :wink:
Your Ruckus APs are capable of over 1Gb/s on 2.4Ghz (faster data in the 5Ghz range) so I think if you were in a lab environment, you would see that speed. In a home, maybe a little less but still, should get more than half.
Do I think this warrants investigation? Absolutely! When a customer is told their product is capable of Gigabit networking, and they have that bandwidth confirmed, to said device, but the device indicates otherwise, something is incorrect. And when various devices, of same manufacturer display inconsistent results, from an isolated and consistent source (e.g. lab environment as home isn’t), then I suspect hardware issue - by design?, software issues - buggy code?, false advertising of product capabilities -? and expectations.

Thank you.

But I am getting full speed on my wife’s iMac. So I would say Comcast is delivering the published rate or better.

However, now I need to figure out the speed limitations for each of our computers. There must be a relatively easy way to do so.

Any tips appreciated.

The simplest you can do is probably just check

I have Gigabit fiber. My 2020 MBP sees up to about 500 Mbps over wifi, but when I plug it straight into the AP Extreme with Cat6 cables I see exactly 1 Gbps. That’s how I know my ISP is delivering on their promise and what limitations I incur by relying on an 802.11ac AP Extreme. If it were getting less over Gigabit I’d know there would be an issue with my cables (assuming APExtr and provider OK). My iPhone 12 mini sees a bit less, but my older 2010 and 2013 MBPs as well as my 2016 SE see substantially less which is not surprising considering their older wifi circuitry.

The iMac speed on Ethernet is the one thing that seems very wrong. It has speed potential way above the internet speed. I have a MacPro 2010 that gets 500 mbps via Ethernet which is what my provider promises. I recommend you download Helios Lan Test
Set up File Sharing in System Preferences > Sharing on your wife’s iMac. Then use Helios Lan test from the other macs to test your local network. Disable the Print test. Take the Internet connection out of the loop.

Another thing: With booth iMacs on Ethernet. Have a look at the iMacs System Preferences > Network > Advanced> Hardware. Is there a difference?

There’s an app, MacPilot - Koingo Software, Inc. | MacPilot 12: Unlock 1200 features in Mac OS X

It has a Network Optimisation tool built into it, perhaps of interest or use to you.

For your iMac and its Ethernet speeds, I suspect that cabling may have something to do with it. If you are using older cat 5 cabling somewhere in the connection between the computer and the router, it could be the limiting factor, as it’s limited to 100 mbps. The iMac itself should be capable of gigabit.

If the cable path is going through a switch, it may be the switch; cheaper ones are limited to 100 mbps for each port.

You can also configure specific router Ethernet ports to 100 though that’s usually something you have to override yourself when you set up the router, so it’s probably not that.

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I think @ddmiller makes a very good point. If you know your provider is delivering, your Mac should be able to match those speeds over Ethernet. If you don’t see that, then it’s almost 100% certain it’s the cables or the router in between.

Another thing to check are the physical portion your various devices and connectors on the cables. I was getting slow connections when using one of my switches until I applied a bit of contact cleaner which brought devices connected there up to snuff.

There are several sites that make it easy measure your Internet connection speed ( for example). To measure the peak network performance of your own computers or equipment, a tool called “iPerf” is commonly used.

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As @psichel said, iPerf3 is a good tool for finding bottlenecks in your LAN. If you have Homebrew, it’s even easier to install. JPerf adds a GUI, though I’m not sure how up-to-date it is.

I wouldn’t worry too much about Cat6 cable. This article suggests that many cables labelled Cat6 – even “big brand” ones – do not even pass Cat5e performance tests. On a gigabit link (2015 MacBook Pro) I measured 750–825 Mbit/s over 13 metres of cable that is literally as thin as a bootlace.

I’d suggest that whatever is responsible for the low bandwidth on some of your Macs, it isn’t the Macs themselves and it isn’t the cable (though as @aforkosh said, cleaning connectors might be a good idea). Good luck!

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