Q: BUG: Mountain Lion kills wifi speed when using airplay or time capsule

Same problem here... It's just horrible. Networking run's fine on WIFI until Timemachine is starting. WIFI speeds drops to almost zero on my 802.11n network on my Mac. It's horrible! Never had this issue on Lion.

On ethernet it works fine. However, have no option to run a ethernet cable through the whole house.

I can confirm that 10.8.1 does not fix my Fall 2007 MacBook Pro's wi-fi AirTunes stability problem.  Back to Ethernet!

Same problem here. Mid-2007 MBP, just upgraded to Mountain Lion, Time Machine is essentially toast. Backups never complete. Wifi transmit rates bounce between 6 and 15. My other two more recent Macs are getting 200-300.

Thanks for conducting proper testing, Apple.

FWIW, I've found that turning the wifi off, the immediately back on will fix the issue, but only for that backup.

Foxxyben wrote:

 

I am also having the same issue on my 2007 Macbook Pro.  FWIW, I've found that turning the wifi off, the immediately back on will fix the issue, but only for that backup.

Good call. That definitely helps.

This issue also affects update downloads from the app store.  Updating iMovie started at a Transmit Rate of 6. Stopping and starting the WiFi allowed the Transmit rate to go up to 216.

Just something else to add to it.

10.8.2 is out and it doesn't fix this problem.

I know I'm wasting my time asking, but anyone have a dependable workaround for this? I've tried some that I've found in the forum, but nothing seems to work.

I don't understand why the transmit rate can be so low and the "Internet speed-check" not drop. Also I'd like to get my time machine back working via WIFI (yes it works OK with an Ethernet connection). Manual backups to the portable HD are becoming bothersome.

At any rate, I thought I'd check to see if anything new was found.

Thanks in advance.

justin_case wrote:

 

I know I'm wasting my time asking, but anyone have a dependable workaround for this?

Yes. Change the wireless radio mode on your router to 802.11a / 802.11b / g .

The problem only exists due to a flaw in the Mountain Lion networking 'n' subsystem code which does not communicate correctly with the Airport card in the MBP3,1.  Apple has not addressed this issue, and it's open to debate how much effort they will expend to support 20 dollar software running on a 5-year-old laptop.

Disabling the n on your router bypasses the problem at the expense of network speed. Although the speed will be limited to 54Mbps, it will at least be stable.

The only other workaround involves repeatedly turning the Airport card off and on until a good connection is obtained, but as others have noted, it doesn't stick and must be repeated whenever the problem reappears. I've found that using WiSpy from mkdsoftware [dot] com (free) is useful to me as it constantly reads the "Transmit Rate" from the connection and displays it on the Menu Bar, so you can see at a glance when the Transmit Rate drops.

Good luck.

aysm?,

Thanks for the useful info. Could you tell me how you found this out? Did Apple Tech Support tell you this or do you have access to Apple bug reports?

And as for Apple not addressing this problem because our laptops are 5-years old, well, considering that the "n" subsystem code worked perfectly fine in all previous versions of OS X, then maybe they should be less sloppy about their coding. But yeah, I'm not holding my breath.

In the meantime, I'm not goin giving up network speed in order to start using Time Machine again. I just have Crashplan backing up to one of my network hard drives. It works just as well and uses less overhead than Time Machine.

Thanks.

Gunny Sack wrote:

 

Thanks for the useful info. Could you tell me how you found this out? Did Apple Tech Support tell you this or do you have access to Apple bug reports?

Apple tech has been no help, and I do not have access to the bug reports. However, replacing the .kext files in System/Library/Extensions with those from Snow Leopard restored the 'n' connectivity for me. It appears that either the correct Atheros file is missing in ML, or the replacement Atheros file is just wonky; in either case, restoring the files from SL did result in a working 'n' subsystem

I'll take no responsibility for anyone killing their OS by replacing the files - do so at your own risk - but to read up on the procedure, I found discussion and procedures elosewhere by google/binging "Wifi doesn't stay connected with 2010 MacBook Pro after upgrade to Mountain Lion"

Aysm,

Thank you...That worked...I'm still a little PO'ed at Apple for ingoring the problem...and they just turned my Airport Extreem into b/g device...Thanks Apple for the downgrade.

But you did get my Time machine back up and working, so I think you very much.

Apple, wake up! No one cares if it's only $20, they want thier devices to work....

aysm,

Thanks for the tip.

I'm going to try the Atheros kext downgrade. First I'm going to try the kext from 10.7.3 since I didn't have TM or Airplay probems with Lion. If that doesn't work, I'll try to the Snow Leopard version.

Here are some links I found that others, should they decide to try this, will find useful:

Kext Wizard - Easy to use Kext Installer and more

Mac OS X 10.7/10.8 Wi-Fi problems and the fix

v3.2 Atheros Wi-Fi driver from Snow Leopard, to use on Lion

Following aysm's suggestion, I downgraded the wifi kernel extension for my MacBook Pro. Since then, Airplay and Time Machine have been working flawlessly, with no slowdowns in transmit rate. I've been streaming music to my Apple TV ever since.

I downgraded the Mountain Lion Atheros kernel extension (IO80211Family.kext - version 5.0) to version 4.1.2 from Lion 10.6.3.

And if I run into problems with that, I can still downgrade to the kext from Snow Leopard.