Ever since 10.8.x came out, some people (including myself) have had major issues with Wifi on our Macs. The problem has existed since 10.8.0 and still exists in 10.8.4. Over time (sometimes within 10 mins), the Wifi transmission speed will gradually drop down to 2-4, and transfer speeds will drop accordingly, and not recover without a reboot.
The following conditions seem to cause this bug:
- 802.11n (either 2.4ghz or 5ghz) wifi connection (does not seem to affect 802.11a/b/g)
- Large transfers such as Time Machine backups, AFP/SMB file sharing
- Confirmed some models of MBP 2007 15" (MacBookPro3,1), and some late models of MBP Unibody 2011 15"
- Happens on Apple Airport Extreme (any generation) or 3rd party APs
Rebooting fixes the problem for a while, until the large file transfer happens again.
From 10.8.0 till 10.8.3, the fix was to take 10.6.8 or 10.7.3 IO80211Family.kext files and swap it in. The connection issue would go away and performance would be snappy and quick like it was in 10.6 and 10.7.
In 10.8.4, Apple made some changes for various reasons, which ended up breaking Wifi pretty badly if you tried the kext swap.
I needed to fix the problem since I couldn't back out to 10.8.3. I spent a few hours rummaging around through OS X's guts, swapping out files, changing settings, messing with permissions. I discovered that the problem was related to changes with /usr/libexec/airportd. Swapping the 10.8.4 airportd back to the one included in 10.8.3 restored Wifi.
I did a posting here on Apple's support forums detailing my part of the fix that makes the kext swap work again. Unfortunately, took a little while for people to realize what I was talking about. But, once they did, and tried my fix, I was getting positive feedback.
I've made a zip file of everything users who are suffering from Wifi problems need in order to get back up and working. You can get it here. It includes the 10.6.8 and 10.7.3 IO80211Family.kext files, as well as the kext utility you need to install them, and the 10.8.3 airportd binary that you can use to replace the 10.8.4 one.