You may have already done this - Be sure the WIFI if off on the the iMac, power off the modem, router and iMac. Disconnect the the other Ethernet devices. Power up the modem and wait for it to stabilize, then the router waiting for it to stabilize, and then power up the the iMac, and then test the speed. Also sign on to the modem and see if there are any error messages in the log and see how many up and down channels Comcast is giving you. Are you also getting an IPv6 connection?

@ArcherC8 

 

Thanks!  

I troubleshot quite a bit last night, and seem to have figured out that the slow wired speed is only happening on a 2010 model Mac Mini.  My 2018 model is getting 600-700, more appropriate speeds.  They both have gigabit capabilities, but I think the older computer is just testing slow because of its own speed to write and read the test files.  Slower processor and hard drive, seems to be the culprit.

 

I did cycle all the equipment on slowly and in sequence like you mentioned.  Thanks for that!  

Wireless is still a bit sporadic, but is testing better than before.  I also found that the detailed info visible by option+clicking the wifi icon is much different from the speed tests.  Tx rates in that drop-down are much faster, so again, slow speed is likely a result of the computer's power.  Testing speed seems to follow the power of the wireless device.

 

IPv6 is available on the LAN, but I believe IPv4 is what's being used at the moment.

A lot of Apple users do not know about the option + WIFI icon and then clicking on diagnostics and then clicking on window (upper left - not continue in the box) to see the tools and stuff. When you run the speed test, most show if it was IPv4 or IPv6. Also you can go to https://test-ipv6.com/ which will check your IPv6 connection. For the mini, go to the system preferences, network, Ethernet, advanced, hardware and see what the settings are.

@ArcherC8 

 

Very helpful, thanks!  

So, IPv4 is what everything is running.  I can get v6 set up, but I'm not super familiar with the advantages in performance.  Security, I get that part.  Google explains some others, as well.  If there's something really compeling outside of the security of it, I'd be interested to hear.

 

*Side note - Any opinions on WiFi Extenders vs Powerline Adapters?  I need a boost on corner of my house, and initially assumed an extender would be best.  Reading up on them a bit though, the Powerline option really looks like it could be better.

 

Thanks again for the info!  I know enough to get by on this stuff, kinda learn what I need as I go.

 

-Wayne

The IPv6 as I understand is more of a thing we will need in the future for addressing. I have noted that when I run Comcast's ISP speed test it seems to default to IPv6. Do they do that because it is faster possibly because it is less used or is it just faster? I just tested my Xfinity 200 service and got about 235 for both protocols. I have an extender to cover a dead spot (RE220). I needed coverage more than speed. My house layout would not allow running a Ethernet cable from the router to the extender. I would have got a powerline extender if I could have run the cable. There is a speed loss using a WIFI connected extender. I set the extender to use one channel to transmit and the other for the backhaul. When it gets time to replace my router, I think I will get a Mesh system.