Mac OS X 10.5 (Leopard): Kernel panics related to specific USB devices

Posted by Pierre Igot in: Macintosh
February 3rd, 2008 • 11:53 am

The situation regarding system stability and reliability in Mac OS X 10.5 (Leopard) is a bit of a mixed bag. On the one hand, the system has been quite stable in my experience, which is pretty good for the first or second version of a new product. (Everything is relative: In an ideal world, system stability would be a given. In the Mac OS X world, things are much better than they used to be in the classic Mac OS world, but there are still lingering stability issues, mostly related to hardware problems.)

On the other hand, some people are indeed experiencing a high number of kernel panics on a regular basis. I was one of those people, as I indicated in a post in November 2007. The panics would either take place while I was working at the computer, with the usual grey overlay and multilingual message. Or they would take place while the computer’s display was asleep, and then I would be unable to bring the display back from sleep.

In both cases, I had no choice but to do a hard reset. Sometimes after rebooting the machine I would get a panic log. Sometimes I wouldn’t. When I would get a panic log, it would usually point to USB issues as the source of the problem, with multiple references to “” and other parts of the OS involved in managing USB devices.

This led me to do some troubleshooting, by eliminating some USB devices and by reorganizing my USB device chains. And after several weeks of panic-free computing with Mac OS X 10.5, I can now confirm that, in my case at least, the culprit appears to have been an Apple USB modem connected to my phone line.

I don’t use the Apple USB modem for connecting to the Internet. I only use it in conjunction with Apicmac’s Caller ID software. The software serves a single purpose, which is to display the caller ID information for incoming calls as a notification in big characters on the screen and keep a log of that information. (It is also smart enough to identify incoming calls coming from phone numbers that are in your Address Book and display your Address Book information for the numbers when available.)

This use of the Apple USB modem with Caller ID was a convenience for me, because the caller ID display on my phone/fax machine is a small LCD screen that can only display one line (so it can’t display both the number and the name at the same time) and I have to get up to look at that LCD screen, because I keep this phone/fax machine out of the way. As well, the caller ID functionality of this machine is pretty defective and the machine only displays the caller ID information half of the time (at best), even though the caller ID information is readily available and appear on other phones with caller ID displays in the house. The combination of the Apple USB modem and the Caller ID software was much better at displaying the caller ID information reliably.

But it was not exactly an indispensable part of my daily workflow. And through weeks of careful troubleshooting, I have been able to determine that indeed it was when the Apple USB modem was plugged into my Mac Pro that I would get the kernel panics. I did not plug the USB modem in for several weeks and did not have a single kernel panics. I plugged it in again a couple of weeks ago, and got two kernel panics within 24 hours. I unplugged it again and haven’t had a single kernel panic since (except for one when I put my wife’s iPod mini on my iPod video’s FireWire dock and obviously did not push hard enough, so that the iPod mini was only half plugged in and Mac OS X did not like that at all).

I think this evidence is pretty conclusive: In my case at least, the source of the kernel panics in Mac OS X 10.5 is the Apple USB modem. It is an annoyance, because things worked just fine with the Apple USB modem and the Caller ID software in Mac OS X 10.4 (Tiger), and it is quite disappointing, since the modem is made by Apple and I would think that it would be properly supported and tested (although I don’t suspect that there are many Macs in Apple’s testing labs using a USB modem these days).

But, like I said, I can live without the caller ID functionality for now. I still hope that Apple will review my bug reports carefully and address the problem eventually in a Mac OS X 10.5.x update. But there is no sign of this happening so far.

What is more worrying to me is that my problem certainly does not seem to be an isolated case. I have a friend who is running Mac OS X 10.5.1 on a PowerMac G5 Quad, and she too has been experiencing kernel panics on a regular basis. In her case, there is no Apple USB modem involved. The culprit appears to be a seemingly innocuous Dymex USB 2.0 hub. If she uses it, her G5 Quad panics on a daily basis (either while she’s working or by failing to wake up from sleep, just as in my own experience). If she removes it, the G5 Quad no longer panics. Again, it’s pretty conclusive evidence. But her USB hub is more important to her than the USB modem is to me. She needs it for her various USB connections. She could try to replace it with another USB hub from a different manufacturer, but what guarantee does she have that the new hub won’t cause the same problems?

There is no page on Apple’s web site indicating that some USB devices are not supported, for obvious reasons: These devices should be supported. They certainly should not be causing kernel panics on a daily basis!

Sadly, this appears to be the situation right now. A quick search for “USB kernel panic” in the Mac OS X 10.5 forum on Apple Discussions shows that there are certainly more than a few people with similar problems, with a variety of USB devices.

Some people indicate that they already had problems in Mac OS X 10.4, but certainly there seems to be a surge in problems with kernel panics and USB devices in Mac OS X 10.5. This is quite distressing. What about those people who rely on their Apple USB modem for their Internet connection? Or those who, like my friend, really do need a USB hub in order to be able to connect their various USB devices?

Apple needs to take a long, hard look at those reports and really take this issue seriously, with a fix for Mac OS X 10.5 as soon as possible. Let’s hope that they are currently working on it and that it won’t be long.

2 Responses to “Mac OS X 10.5 (Leopard): Kernel panics related to specific USB devices”

  1. henryn says:

    Hmm, I just helped a technophobic friend move up from an old G4 tower running MacOS9 to a new Intel iMac running 10.5 –quite a jump, especially for a technophobe– in her home office.

    She would not have upgraded at all except she uses AOL for email, and they finally convinced her that there would be no more upgrades for the OS9 email client!

    All went well, except that there is simply no apparent way to bring her old emails forward.

    But I’m writing because a secondary goal was to replace a klunky old HP Fax machine. I bought her an Apple modem, we installed it, and tested an exchange with the HP Fax. No problem!

    Reading this, I’m now very concerned that I’ll get a Technophobe Panic call from her when a kernel panic occurs. All this technology is difficult to handle for technophobes when it works correctly! I’m not eager to explain Kernel Panics to her, not in the least.

    Well, looking at the bright side, this is a very similar system to yours, I think, and it is very conservatively kept, with minimal add-ons. So, if it is stable and yours isn’t, maybe that will be useful information.


  2. Pierre Igot says:

    Henry: I doubt that all machines using the Apple USB modem are affected. Otherwise, there would be quite a stink and Apple would definitely have to do something about it! It is probably only when using the Apple USB modem with certain configurations. How many Mac Pro users use an Apple USB modem?

Leave a Reply

Comments are closed.