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Very Slow broadband completly specific to iMac

My late 2012 iMac running Catalina 10.15.7 (the latest version available) has very slow broadband download speed.


It is the iMac, not the network. All phones iPads, MacBook and windows devices receive about 70 Mb/s when placed immediately next to the iMac.


The iMac receives at about 3 or 4 Mb/s whether it is on wifi or ethernet. Curiously it has the same upload speed of about 12 Mb/s as everything else.


I have downloaded a copy of Crome specifically to see it it was a Safari issue - It isn't, Crome shows exactly the same speeds.

As The copy of Chrome was downloaded just for this purpose it was clean with nothing in any caches or history, so at least I have discounted Safari itself as the cause of the problem.


I am guessing there is some setting, or such like, that is wrong, but I haven't a clue what it may be.


Any ideas what I should be looking for, gratefully received.


Many thanks,

David.

iMac 21.5″, macOS 10.15

Posted on Jun 2, 2023 9:00 AM

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Similar questions

13 replies

Jun 5, 2023 10:20 AM in response to David Gee1

After each change to Mac OS you should be doing the following to verify:


  1. Restart Modem
  2. Restart Router
  3. Restart Mac in Safe Mode (may take 10 minutes or slightly longer) and then restart normal.
  4. Test


This would be considered more thorough troubleshooting than simply making a change and thinking it will work. It simply means you are starting from the same base point when making a change and giving the system the opportunity to "take" the change. Yes it is more tedious however it is more thorough.

Jun 5, 2023 12:12 PM in response to David Gee1

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files


NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.


Jun 2, 2023 9:49 PM in response to David Gee1

Make a New Location, Using network locations in Mac OS X ...


System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.


System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.


The interface that connects to the Internet should be dragged to the top of the list.


Sys Prefs>Network>highlight the Interface you're using>Advanced>TCP/IP>Configure IPv4: Using DHCP.


If using Wifi, instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.


System Preferences>Network>choose interface>Advanced>Proxies Tab, make sure none are set, like for HTTP & HTTPS.


System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...


8.8.8.8

8.8.4.4

1.1.1.1

9.9.9.9


Apply.

Very Slow broadband completly specific to iMac

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