Freezing G5 Quad: Can still log in remotely via ssh

Posted by Pierre Igot in: Macintosh
September 23rd, 2006 • 5:37 pm

I’ve now switched back to the G5 Quad as my main machine and did a clean install of Mac OS X 10.4.6, just in case the 10.4.7 update played a part in the problem. I reinstalled all my software and used SuperDuper! to update my documents partition to match the one on the G4 MDD. I also didn’t reconnect my second display (the 23″ one) right away. And then I started using the machine again.

Sure enough, I got a freeze within 24 hours. The freeze occurred while working in GarageBand. Not only did the whole screen freeze (including the mouse pointer), but the audio playback of GarageBand itself also froze and started repeating a loop of sound endlessly.

Out of curiosity, I went to my G4 MDD and tried logging in remotely via ssh, since I had activated remote login on the G5.

Much to my surprise, the G5 was very responsive and allowed me to log in without any difficulty. I was then able to run the top command in Terminal, and the list of processes looked perfectly normal, with top itself at the top with more or less 10% of CPU, as expected, and the other processes still running, without saturating the processors or anything.

The fans on the G5 Quad soon kicked in, indicating a loss of control of the temperature monitoring process (and the red LED came on in the front), but based on what top was telling me, behind that frozen façade the machine was still running just fine.

I don’t know enough about using Terminal to monitor a machine remotely to do much beyond this, however. I don’t know if there’s an easy way to see if one particular process is frozen.

I tried to shut down the machine remotely using shutdown -h now, and the shutting down sequence did begin on the G5, based on the feedback I got through Terminal… but it never did complete, and ultimately I had to do a hard reset of the G5 just the same.

I find this quite intriguing. It certainly seems to indicate that the temperature controls are involved, but that the core of the machine (the CPU, the RAM, the hard drives) are not directly affected by these freezes.

Still, that doesn’t tell me what to do to avoid the freezes or indeed to trigger them reliably.

I got on the phone again with Apple, and inquired about whether there was anything that I could try and do remotely via ssh when a freeze happens, but the tech support representative didn’t have any suggestions. He didn’t seem to think that there was anything that could be done via “software” (his words) and that my clean install of Mac OS X had pretty much ruled out a software issue anyway.

So now I really do have to take the machine to the repair shop and try and see if they have any other, more powerful diagnostic tools that could help them identify the source of the freezes. I will set up an appointment on Monday and will just have to drive there (a six-hour round trip), I am afraid.


3 Responses to “Freezing G5 Quad: Can still log in remotely via ssh”

  1. Arden says:

    Sounds like a bad motherboard.

  2. indiedan says:

    It might be fun to see what
    $ ps -A
    comes up with. I’m no ps expert but that should give you a list of every process and their state – Zombie, Sleeping, Crashing etc…

  3. Pierre Igot says:

    Well, I don’t know if the ability to remotely log in was a one-off, but I got another freeze today and I most definitely was not able to log in remotely. (I got the message that the “host was down.”) I’ll keep trying, but it doesn’t look likely to be a realistic troubleshooting avenue. (Come to think of it, when the “freeze” turns out to be a kernel panic, which it does quite often, I really don’t see how remote login can continue to work.)

    The repair shop guys are very gracious and have offered to pre-order replacements for the parts that are likely to be involved here (logic board, etc.) and then set up an appointment once they have received the parts, so that I only have one trip to make (with diagnosis and repair all at once). Apparently they can return the unused replacement parts to Apple after that.

    Let’s hope they get the parts soon and get this fixed once and for all soon.

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