PowerBook G4 Double-Layer SuperDrive Special Report: Lapses in AirPort connectivity; Sudden drop-offs in network throughput

CNET staff

Sept. 2, 2009 8:27 a.m. PT

8 min read

There are two primary categories for cases of lapses in AirPort connectivity, sudden drops in signal strength or complete loss of connectivity until a restart is performed -- those caused by the presence of 1 GB of RAM and all others.

The 1 GB or more of RAM issue An issue where some mid-2005 iBooks with more than 1 GB of RAM spontaneously lose AirPort connectivity may also manifest on Double-Layer SuperDrive PowerBooks
One reader writes:

"Having this problem on my (obviously brand new) PowerBook 17" DL-SD. I picked it up Saturday at the Apple Store, could not purchase more RAM in the Store (they claimed the DDR2 RAM was too new), so ordered it online. I was running this machine for three days with no problems except it's been ungodly slow (I'm coming over from a 1.67 MHz 17" with 1.5 GB RAM; moving down to 512 MB was a killer). The DDR2 RAM arrived today, I installed it tonight, and within an hour started having, in a chronic manner, the sudden loss of AirPort as described on MacFixIt

"All the symptoms are the same: CPU spike, specifically kernel_task, which hits 70% of the CPU and above; loss of connection and inability to regain, even from another account; jerky cursor; and a fix from a reboot.

"This RAM is fresh from Apple, and one of the 1GB cards even has their logo on its sticker.

Dozens of owners corroborate.

When this issue presents itself, the kernel-task process spikes in processor usage, and AirPort connectivity is suddenly lost.

Note that while there are numerous alternate causes for lapses in AirPort connectivity including outside interference, improperly seated wireless cards and more, this particular sequence of events appears to be a unique hardware-related issue.

In almost all occurrences of the issue, afflicted PowerBooks (and iBooks in the former case) have more than 1 GB of RAM installed. Memory fault by manufacturer does not appear to be a cause, as users with various brands of memory -- including Apple's own -- are suffering from the problem.

The problem is most likely to occur, it seems, under heavy network traffic conditions or under unusually high processor loads -- both of which can sometimes be generated by the use of Java-based peer-to-peer applications like LimeWire and some BitTorrent clients.

MacFixIt reader Elliot Zaret writes:

"I have the PowerBook 17" (Double-Layer SuperDrive) with an extra 1GB RAM (third party). A couple times a day, the kernel_task process suddenly spikes taking up more than 65 percent of my CPU and I lose airport connectivity. At that point, the computer is basically unusable since it is so slow with the kernel_task using all the CPU. Turning the airport on and off doesn't help, nor does logging off. Only restarting seems to fix it (which is obviously a pain.) I've run the Hardware Test a couple times and it has found no problems with my memory (or anything else)."

MacFixIt reader Michael reports losing his connectivity while using a BitTorrent client:

"In regard to the comment on new powerbooks with Double-Layer SuperDrives losing AirPort connectivity, I have the same problem. I have a 15-inch with 1.5 GB of RAM (this is non-Apple). It's fine for Web, and World of Warcraft use, however i permanently (until I restarted machine) lose Airport connectivity if i try to update wow using its updater software, and the same with all BitTorrent clients -- I lose my connection and cant get it back until performing a restart. I am using WEP security on a Wireless 802.11g router."

Another reader reports the same -- with Apple's BTO RAM:

"My new 15" PowerBook came in yesterday with 2 GB of RAM installed by Apple (I know... cheaper anywhere other than Apple... but my company paid for it, so who cares). I noticed loss of Wi-Fi after I started using 2 different BitTorrent clients on my other computer. It didn't happen when I used BitTorrent, but did when I used BitTorrent in conjunction with Azureus. I also noticed it when I was configuring Virtual PC this morning."

Matt Williamson reports use of several processor intensive applications right before the loss of connectivity:

"I experienced this for the first time just yesterday. I picked the new PB up last Friday night, but didn't start using it in earnest until this Monday. I'm running 2 GB of memory. I've seen the problem twice. The first time (Wednesday, I think) kernel_task never exceeded 20% of CPU time. It happened yesterday, and kernel_task hovered around 50%. Jerky cursor both times, and both times, a reboot was required. On both occasions, I was playing music and downloading TV shows in iTunes, while doing various other things."

MacFixIt reader Geoffrey adds:

"I purchased the unit with 1 GB of RAM and upgraded with a Crucial 1 GB DDR2 chip and have the sudden loss of airport connectivity with associated cursor weirdness and the exact symptoms listed on your webpage (1x/day). Very annoying but fortunately dealt with a restart. Would love to know when there's a work around. Interestingly, it only seems to have happened so far (crosses fingers) at home and not with my work wireless network (both apple products, the latter only an airtunes express)."

Another reader having the problem reports some odd changes to his system's IP address after connectivity is lost:

"I had 1 GB in my High-res 17" PowerBook and just installed a second 1 GB for a total of 2 GB. Suddenly, I have the sudden loss of airport connectivity problem in spades. I can stay connected for at most 5 minutes before the connection fails. If I connect through Ethernet, the problem does not occur.

"After the problem happens, my IP address in the Network control panel has changed from being in the 162.198.0.xxx range to one in the 169.xxx.xxx.xxx range. It is very difficult to get this to change back to one in the correct range.

"I have it set to configure IPv4 Using DHCP and my router address is 192.168.0.1, which is pretty much plain vanilla."

Ben Muldrow adds:

"I bought my new 17 inch powerbook yesterday, the 2 GB of Ram arrived 30 minutes ago, not more than 5 minutes after installed, airport died and a kernel task started eating 60% of CPU power and everything was jumpy."

lookupd workarounds may be effective In some instances of this issue, the workarounds listed in our "Fixes for system-wide freezes when Web browsing [avoiding lookupd bug]" tutorial may be applicable -- as it appears that this particular issue generally also results in a stall or complete hang of the lookupd process.

These workarounds include temporarily turning off your AirPort card, resetting lookupd via the Terminal, deleting the lookupd cache, killing the crashdump process and more.

Also note that the developers of the popular utility Tiger Cache Cleaner recently added the ability to optimize some settings of lookupd -- including flushing the lookupd cache and the ability to restart the lookupd daemon.

Running these processes regularly can, in some cases, work to avert this issue.

Repeatable solution: Reducing RAM The only surefire solution to this issue is to reduce the total amount of used RAM to 1 GB or less.

There are two ways to reduce the total amount of usable RAM:

Physically remove module(s) until the total amount of installed memory is 1 GB or less

Enter the following command in the Terminal (located in Applications/Utilities) followed by the return key: % sudo nvram boot-args="maxmem=1024" -- this limits the amount of memory usable by the system.

Upgrade to Mac OS X 10.4.3 It appears that for some users, Mac OS X 10.4.3 helps reduce occurrence of this issue.

However, not all users have noticed the improvement.

One reader writes:

"Just a note from France, where it seems that the Powerbook here have also the very same problem : A friend and I just got our 15" PowerBooks with 1.5 Gigs of Ram. We cannot connect for more than 2-3 hours to WiFi Networks : performance drops, cursor moves strangely, and the connection drops rapidly.

"Applying 10.4.3 does not fix the problem.

"Connecting to the net with a RJ45 Wire and turning airport off seems to be a way to avoid the problem."
The other cases As aforementioned, there are many other causes for lapses in AirPort connectivity or degradation in signal strength. Some general observations about the manifestation of these non-RAM-total related issues:

"After a few hours of uptime, the AirPort connection will start slowing down, usually to around half a megabit of throughput, which slows not only the Internet but also local networks

After ~24 hours of uptime, my airport connection will begin to drop in and out

The issue occurs multiple AirPort Base Station networks, with graphite, snow, extreme, and express models of the base station

The issue occurs on both 802.11b, b/g, and g-only networks

Turning AirPort on and off does not fix the problem, but a restart will in some cases

Solutions

Firmly seating the RAM Some users have reported that firmly re-seating the RAM in their PowerBooks/iBooks may help resolve one cause of this problem.

Dave Leary writes:

"I completely removed the 2nd 1 GB memory stick I had installed, checked Airport functioning (it worked perfectly) and then reinstalled the memory card.

"What I did differently this time was that I seated the card quite firmly before I 'folded' it down into the latches.

"Airport has been working just fine for 6 hours now, with no signs of trouble. Previously, 5 minutes was the longest period of connectivity I could get. I know that 6 hours does not make this a proven cure, but it is so much better than previously, and the price is right."

One reader writes:

"Reseated the RAM (2x1gb Crucial) after a good old wiggle up and down, shoved it in good and tight and... I've had six hours without an interrupted Airport connection."

Resetting PMU Users have also corroborated, in increasing numbers, resetting the PMU as a workaround for this issue.

MacFixIt reader Adam Karneboge writes:

"I wrote in over the weekend. I was able to fix my problem by resetting the Power Manager on my new 15-inch high-res PowerBook, which also resets the PRAM and NVRAM at the same time. I have been downloading fine over AirPort both on the internet and from servers on my LAN for two days now without constant background activity."