I have a 2011 iMac 21.5". 3.06 GHz Intel Core 2 Duo
I mainly use wireless but it is still super slow when I switched to wired.
It has not always been slow. This just started a couple months ago. About the time I was having a lot of trouble with my Mediacom service. Which is my I initially thought it was Mediacom. But I have fast speed on my other devices when connected to the same Airport Extreme.
Can you temporarily turn off Virus Barrier to see if this is slowing your system?
Also in your iMac's Applications folder, locate the Utilities folder, open it and look for and launch Activity Monitor.
Look at the Processes Tab and see if there is anything that is using a high percentage of your iMac's resources.
Also, it may just be you need to install more RAM memory.
if your iMac has a 3.06 Ghz CPU, then it is NOT a 2011 model, but a 2010 model iMac.
OS X especially versions 10.7 Lion and 10.8 Mountain Lion use a lot of CPU, GPU, RAM and hard drive resources.
The base 4 GBs that came with your iMac is not an ideal amount of RAM, but just enough to give sufficient operation of your iMac out of box.
OS X, by itself needs between 2-4 GBs of RAM to operate smoothly and efficiently on its own.
Start running extra applications on top of this and there will be more and more slow down of your iMac.
Your iMac can take up to 32 GBs of RAM.
I recomend installing, at least, another 4 GBs of RAM. If you can afford to install more, great then do that!
But you could just start with only an additonal 4 GBs of RAM.
You should see a speed improvement by just doubling the amount of RAM memory.
Here are the RAM specs for your 2010 iMac.
32 GB (Actual) 16 GB (Apple) Memory Slots 4 - 204-pin PC3-10600 (1333 MHz) DDR3 SO-DIMM
You can purchase reliable Mac RAM online from Mac RAM vendors Crucial memory or OWC ( also known as macsales)
Actually I remember when this started happening.
I had been having a lot of problems with my Internet provider, Mediacom. They had just been out to replace my modem with a new DOCSIS 3 modem/router. It's a Netgear. I
This fixed my speed issues that I was having at the time. However I wanted to use my AirPort Extreme for my router. So the only way I could connect my airport to the Netgear was to put the Airport into bridge mode. This worked. But then this issue came up.
Today I disconnected my AirPort Extreme and am only using the Netgear. But I am still having the issue.
If you can access the apple website using the IP address and it loads fine, but when you type in the actual domain name www.apple.com it causes a slow load, then it is definately related to DNS. 126.96.36.199 is google's public DNS and should work if, for some reason, your mac is not getting DNS requests correctly from the mediacom router.
Could be internet plug ins....
Try this - launch safari. Reset safari, by clicking on the word safari beside the apple, then "reset safari". Uncheck "Remove saved names and passwords" and "Reset Top Sites", but keep everything else checked, and reset it then quit safari.
- click finder in the dock, so the word finder appears beside the apple. Also note in the top menu, is the word "Go", click the go menu and then hold down your option key on your keyboard. This will make a "library" appear under your home in the Go drop down. Select the library, then go to your the safari folder. Inside here, drag "webpageicons" to trash.
- go back one screen and select the "preferences" folder - drag "com.apple.safari.plist" to trash
- go back one screen and select the "internet plug ins" folder - this folder should be empty. If it is not......drag what you see out to the desktop....not the trash, just in case you find you need one of them.
- launch safari and test it now