Yesterday we covered reports of an issue where having more than 1GB of RAM in a Mac or PowerBook with an AirPort Extreme card could result in wireless network slowdowns and disconnections, especially during periods of heavy network transfers. According to those experiencing the issue, removing RAM to reduce the total installed RAM to less than 1GB fixes the problem.
We've since received a surprisingly large number of responses from readers. Although some readers with AirPort Extreme cards and more than 1GB of RAM have not experienced any problems, a significant number have confirmed this issue. (Note that it's difficult to isolate such issues from the more general AirPort issues that we've been covering over the past few weeks. In this article, we've tried to restrict the discussion to only those users specifically experiencing problems related to AirPort Extreme and large amounts of RAM.)
For example, Ivan Trundle reports that his connection problems occurred immediately after installing more RAM:
"I 'upgraded' my 17" 1.33GHz to 1.5GB RAM from 1.0GB, and I discovered to my annoyance that switching from home to work (802.11b to g and back again) required a reboot every time. At first, the AirPort menu would show no network, then it would show an unidentified network, and other times it would claim that the password was incorrect to join the 'discovered' network (and still no bars). Everything that I tried to resolve the situation failed, other than reverting back to 1GB."
Similarly, Bryan Stalcup notes, "I recently upgraded from 1G to 2G and have had this problem constantly since. Speed Download will trip it almost immediately, for example, but opening a saved workspace with multiple pages in OmniWeb will trip it also."
Doug Keller's own experiments seem to support the "more than 1GB RAM" theory:
"I originally had two 256MB DIMMs in my 15" Al PB (1.25 GHz). I bought two 512MB DIMMs and installed them and had NO difficulty with AirPort whatsoever.
"4-5 weeks ago I bought two Samsung 1GB DIMMs and put them in my PowerBook. Everything ran fine, except that my AirPort connection would randomly drop and only a system restart would bring it back. This was true regardless of what brand of access point I was trying to connect to (Apple or other parties).
"I ran tests with the 1GB DIMMs, putting each of them in each of the memory slots independently and had no problems. But when I put the second 1GB DIMM back in, the random drops would occur once again. Then I found the Apple Discussion thread you were talking about and tested the over 1GB of RAM theory by putting one 1GB and one 512MB DIMM in my PB -- random AirPort drops. Then I put one 1GB and one of the original 256MB DIMMs in my two slots, random drops. I then put one 1GB DIMM in the back slot and left the front slot empty - NO AirPort drops for several days on constant daytime and several hours of nighttime usage. Seems that, in my case at least, the more than 1GB of RAM theory pans out."
Reader PT Withington has had a similar experience and offers his own theory as to the cause of the problem:
"Bought a new AlBook last December with 512MB. Ran like a charm...I added [1GB RAM]. Immediately my AirPort problems started: it randomly drops out after about 2 hours, and nothing short of a reboot will bring it back. (In the meantime, the 3 other computers in our installation continue humming along fine with the same basestation. None of these machines has more than 1G RAM.)... Mostly I was forced to work with a hardwired connection, because rebooting was the only way to get my Airport back once it failed. (This machine is used for page-layout and web design, so has many large programs open and running with lots of state that I cannot afford to reconstruct every time the airport goes out. Typically Photoshop, Quark, GoLive, several web browsers, Mail, etc. are all running. Often it appeared the net would go out when printing.)
"I eventually hit on the thread in Apple Discussions. I have removed the 512MB Apple DIMM from the machine and had no AirPort dropouts since. (Previously, it would drop after about 2 hours. It has been 4 days since I removed the SIMM and no problems.)
"My personal theory is that there is a flaw either in the hardware or software of the Airport that makes it fail when trying to DMA to addresses above 2^30. These addresses come into play as a machine with > 1G RAM gets heavy use and the high physical pages are allocated. A machine with less RAM or lightly used will not ever venture into that address space."
We could provide many, many similar quotes from readers. The number of reports that seem to conform to the same pattern -- more than 1GB of RAM results in AirPort problems; removing RAM to reduce the total to 1GB or less fixes the problem -- has been quite surprising.
Bad RAM doesn't look to be the culprit Some users have suggested that perhaps the problem is faulty RAM. We're suspicious of that idea based on the fact that so many different brands of RAM have been mentioned in reader reports. In addition, we've received a few reports, similar to the following message from "Myster," that seem to cast doubt on this theory:
"I suspected that there was a problem with the DIMM and had it replaced after some difficulty. Its notable that after removing the [extra] 1 GB DIMM I suffered from no AirPort drops at all. After installing the replacement DIMM the problem returned only I don't run into it nearly as often. I've tried everything I can think of to restore the connection from the command line and just turning the AirPort on/off to no avail. The only fix I've found is to restart the system."
Solutions? Ivan Trundle quoted above, reportedly "fixed" the problem on his PowerBook by resetting NVRAM and deleting several preference files:
"As an experiment, I tried 1.5Gb again, but this time resetting NVRAM as well as deleting all AirPort and system preferences, and ran Yasu to tidy up what was left. Ouch. Now it is the way it should be -- seamless. I've switched from home to work and back again without requiring a reboot for the first time. That extra 512Mb SODIMM is here to stay. My advice is to reset NVRAM, delete ~/Library/Preferences/com.apple.systmpreferences.plist and com.apple.AirPort.plist (the latter was not recreated... odd), and run Yasu to clear permissions, caches and logs. Three hail Mary's and a drop of good malt Whisky, and everything is just perfect. Your mileage may vary..."
UPDATE Ivan has since written that the problem is still occuring, indicating that the fix was not successful.
Wayne Fox offers a different suggestion:
"I just migrated to a new 1.5GHz 17" PowerBook, and moved the RAM [from another PowerBook] over. The problem returned. This time, I eliminated all of the connections except AirPort in the [Network pane of System Preferences] for that Location, and it seems to have solved the problem. Hasn't happened since I did this."
Are you experiencing this issue? (If possible, please verify that moving extra RAM fixes it.) Drop us an email at Latefirstname.lastname@example.org.Resources