Q: iMac 12,2 (mid 2011) airport (wireless) problem

I tried to use another channel of my router. Still got the trouble. I checked updates and all are latest. And like Sander81 i got more devices/computers which work fine with the router... No idea... :( hope it will be fixed soon...

So glad i found this thread.

Been pulling my hair out all day trying to figure this out.

at least i know its not just me.

I have tried everything i can think of, nothing works. I thought for the longest time it was my Airport Extreme having problems, unfortunately i am seeing its the new iMac.

Switched between 2.4 and 5ghz with no change.

@Sander81. i have turned the Airport off, and plugged in a plain 802.11n single band netgear router, no difference. unless you mean turning off the actual antennas and just use one.

I also have other Mac's and 1 PC on my network, every one of them is fine, just the new 27 iMac is having this issue.

I hope Apple is aware of the issue and will have a fix shortly.

Sander81/hardbase,

I would try disabling security first and check if it works without security. What channel are you using ? PIck a common channel like channel 36 ( if its a 5 Ghz router) and then test with and without 40 Mhz channel extensions.

If it's a 2.4 Ghz only router, then make sure the router is only using a 20 Mhz channel width.

Let me know if any of these options work and then we can debug some more. Also what signal strength are you seeing the router at ? Holding the Option Key and clicking on AME when connected to the network gives you this information.

Just tried your suggestions, same problems. With and without security no change.

my test is a 5mb mp3 streamed from a USB drive connected to the AE, every device in the house can stream it fine, except the new iMac. generally 8-20 seconds in, 5-15 second pause. a 4 minute song, takes 13 min to fully play this way... annoying to say the least.

hope there is some simple explaination to this that i just don't see.

New iMac 2011 3.4ghz 27". 

Cisco AP1142N a/b/g/n (Autonomous mode)

I have am having the same issues.

1) done a PRAM,

2) SMC reset,

3) Reinstall of OSX,

4) Update to 10.6.7 (imac 2011).

5) I have cleared out related  .plists files in /Library/Preferences/SystemConfiguration

6) Deleted and re-added the network configuration.

In bootcamp with Windows7 , I had absolutely no issues with clean iperf testing at over 100Mbits/s. Works fine with native Atheros driver in the Bootcamp Windows7 partition.   

In OSX, the problem occurs at both 2.4Ghz and 5Ghz 802.11n configurations.  I am using WPA2-AES (PSK) for security.  In OSX, while using WPA2-AES (802.11n), I am getting severe performance degradation. Web pages are slow to pull up, and if I am doing a download, pings to local hosts on my lan fail in a terminal window.  Many downloads fail outright.

The problem seems directly related to the use of WPA2-AES.  When I drop down to WPA-TKIP, there are no issues. However, 802.11n standard requires WPA2 for security.  Dropping to WPA-TKIP forces down to 802.11a on my AP in which I run more reliably, however limited to 802.11a rates. TKIP is not allowed with 802.11n per standard. 

This is confirmed on both 2.4Ghz  and 5Ghz. I am using 40Mhz spacing and allowing Dynamic Frequency Selection on the 5Ghz band.

Log entries on my AP1142  during 802.11n +WPA2 AES-CCM are showing the following errors:

May 12 00:07:05: %DOT11-4-CCMP_REPLAY: Client 109a.dd9e.9990 had 16 AES-CCMP TSC replays

May 12 00:07:11: %DOT11-4-CCMP_REPLAY: Client 109a.dd9e.9990 had 28 AES-CCMP TSC replays

May 12 00:07:17: %DOT11-4-CCMP_REPLAY: Client 109a.dd9e.9990 had 21 AES-CCMP TSC replays

May 12 00:07:23: %DOT11-4-CCMP_REPLAY: Client 109a.dd9e.9990 had 6 AES-CCMP TSC replays

No errors at all when running with WPA1 / 802.11a with TKIP.  Performance is actually much better at this speed.

My 2009 MBP with 10.6.7  runs 802.11n +WPA2 AES-CCM without any issues whatsoever. I have run at the maximum 802.11n speed supported by my AP with my MBP without problems.

Have a couple of other 802.11n WPA2 AES-CCM connected devices in my house running without any errors logged either.  Both at 5Ghz and 2.4Ghz bands.

This definitely looks to be a driver issue in OSX.  It needs to be fixed soon otherwise I have to wonder how Apple can claim that this is an 802.11n system when its totally broken.

I solved the "WiFi connectivity drop"-issue of the new iMac 12,2 (May 2011 refreshment / 27" + i7 + 3,4 GHz) by changing the channel of my WiFi-router manually.

Strange, because the new iMac replaced an older one from 2007 that worked at the same place and with the same router without any problems...

what channel did you use?

and 2.4 or 5ghz? etc.

I have had my iMac connected directly for the last 3 days due to this issue.

Tonight i decided to turn on airport and unplug and see if i can mess with the settings on my AEBS again.

didn't need too..

It's working as it should now... nothing has been changed since i posted the pic above. It's been streaming my music in iTunes for the last 30 minutes with no hiccups. Even fired up the software update and transfered a 300 mb folder between two macs... all at the same time.

not sure what happened, but i havn't changed anything on my end. See if it stays this way.

I have an imac 3.1GHz i5 (mid 2011) and its dropping out, my iphone, ipad and macbook pro all work fine just not the imac.

So far i checked out Channel 1,2,4,6 with my Router. I still got the trouble. Did anyone check out the 5Ghz so far?

The thing is that it even drops when i am up- or downloading. So in my eyes it has nothing to do with any sleep-modes. It happens while i am using the web  

And i am not sure but i think that privat sharing with another mac has got the issue as well. I sended some Pings for about 40 Minutes and all worked fine. Then i checked out Screen-Sharing and it dropped. Maybe its not the same issue - not sure, but its something i have noticed so far...

And here i found 2 more threads about this imac 2011 wifi issue:

https://discussions.apple.com/message/15194666

https://discussions.apple.com/message/15190924

I just know that apple (us) noticed about the issue. German Hotline has got no bugfixes or updates so far

Lets hope, wait and see....

gareth97..  Can you provide details on your configuration?

Router  / Access Point Type?

Was this WPA2 or WPA?

What frequency (2.4Ghz/5Ghz) 

Channel number?

Try changing your router to WPA-TKIP to see if the problem still occurs and let us know.

I am Having issues with 5GHz also.  (I have verified that my issue is  on both 2.4Ghz and 5Ghz ).  Are you on WPA2?  Can you test with WPA-TKIP?

Airport Extreme

Channel 9, 2.4GHz, WPA2 personal

Swtich to WPA-Personal  and see of this works.

If you have the AP Extreme,  why not also use the 5Ghz radio? Many more non-overlapping. channels and less congestion.