"shutdown" does "restart"

  1. 400MHz G4 PowerMac (Gigabit Ethernet version). OSX 10.3.9. Been running 10.3.9 since shortly after it was released.

    For perhaps a week now, I have been having the same problem. It happens when I chose "Shutdown" from the menu while logged in and when I just click on the "Shutdown" icon on the login screen. The computer does the usual shutdown routine; it goes quiet for a few seconds; and it starts booting up again.

    This may have happened occasionally in the past. Then again, I may have mouse-clicked on "Restart" rather than "Shutdown" on those occasions. It is completely consistent now.

    I can actually shut the computer down my holding down the power button on the tower during the last of the quiet seconds and the start of the boot-up.

    I cannot tell if this is a hardware or software problem. Doing a "Repair Permissions" with Disk Utility did not help. Running a full diagnostic with TechTool did not help either.

    How do I fix this problem?

    John R Delaney
    MIT Lincoln Laboratory

  2. Do you use an USB hub? I have an iMac G3, and had the same problem. When I installed a small home network, I moved the USB printer to a printer server and disconnected the USB hub, as I did not need it anymore. The problem disappeared.

    _x.

  3. Actually, my hub is not the problem. I tried disconnecting it and nothing changed. No surprise there, as I have had it for some time.

    Another USB device was causing the problem, though, I should have thought of it but just before the problem started, I bought a USB A/B switch so I could share my EPSON All-In-One printer/scanner with my wife's PC. When I unplugged it, the problem went away.

    While on the subject of USB quirks, I should mention that the new switch was plugged into my keyboard which is, in turn, plugged directly into my computer. When it was plugged into my USB hub (and the hub into the computer), I found the keyboard commands for booting from a CD, booting into Open Firmware, etc. did not work.

    I have not yet tried the experiment where I plug the switch into the hub and see if the problem goes away. That one I will try this evening.

    The morale of this story: The PowerMac USB interface, at least for older models like mine, has some very odd quirks that one would not expect if everyone (including Apple) is following the USB 1.1/2.0 specifications exactly. In fact, it seems to be as troublesome as the old SCSI interfaces often were, and broader in the nature of the malfunctions.

    Note to Apple: This sort of thing is NOT good for the Mac's user-friendly image.

    John R. Delaney
    Mildly annoyed consumer

  4. One idea occurs to me.

    I'm not sure whether your model supports this feature: early iMac G3 models (and presumably other product lines such as the PowerMac G4 around the same era) can be started up by pressing a power key on the USB keyboard.

    This is a mechanism which Apple invented to duplicate the corresponding feature available on Apple Desktop Bus keyboards in earlier models.

    It was in violation of the USB standard, so Apple removed support for this feature in later computer models, and removed the power key on later keyboards.

    Looking at MacTracker, it appears the "Sawtooth" PowerMac G4 included the original Apple USB keyboard (with the power key) but the "Gigabit Ethernet" PowerMac G4 switched to the Apple Pro keyboard (without the power key). This implies the Sawtooth supports USB power-on, but the Gigabit Ethernet might not. They might have left the hardware support for this feature in this model and removed it in a later model.

    Assuming it is supported...

    If a USB peripheral was accidentally triggering this power-on signal mechanism, it would cause the computer to start up.

    I have a similar problem with my PowerMac 8600 (ADB) which has an AppleVision 1710AV monitor (had to be repaired twice but much to my amazement it is still going). Sometimes when I shut down the computer, it immediately starts up again. The only way to stop this happening is to unplug the ADB cable between the monitor and computer immediately when I shut down (I also have to hold down the power button on the front to prevent it starting up again).

    Try unplugging all of your USB peripherals immediately after shutdown. If that stops it, progressively add them back again to see if you can spot which one is causing it to happen.

    Assuming I'm right, it is likely to be a timing-critical trigger, e.g. as the residual power held in capacitors in the peripheral drops to a certain level, it does something on the USB bus which triggers the startup signal condition.

    This would agree with your observation that holding down the power button over the "danger period" prevents the computer from starting up again.

    David Empson
    dempson@actrix.gen.nz

  5. Previously, David Empson wrote:

    Looking at MacTracker, it appears the "Sawtooth" PowerMac G4 included the original Apple USB keyboard (with the power key) but the "Gigabit Ethernet" PowerMac G4 switched to the Apple Pro keyboard (without the power key). This implies the Sawtooth supports USB power-on, but the Gigabit Ethernet might not. They might have left the hardware support for this feature in this model and removed it in a later model.

    My G4 Digital Audio (post-dates the Gigabit Ethernet models for those out there not familiar with the various G4 models) does startup from the power-on key on my Kensington keyboard.

    I've never had my G4 restart right away after shutdown, but I've had it spontaneously awake from sleep mode for no apparent reason. (Wake On event type was same as the wake on for a keypress, but no key was pressed.)

    Greg B.

    Actual e-mail address is gbuchner and I'm located at mn.rr.com

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