13 Replies Latest reply: Mar 5, 2009 5:29 PM by brun
brun Level 1 Level 1 (0 points)
I have a PowerBook G4 Ti (Gigabit ethernet). Worked great for years. Today the screen froze in OS X 10.4 while I was working. I had to CTRLCOMMANDPOWER to restart. Upon restart, I only got a black screen after hearing the chime, even though I could here all the hardware running. The only way I could reboot to OS X was by reseting the Powerbook PMU (http://docs.info.apple.com/article.html?artnum=14449#faq8). I am able to use the Mac ok after a PMU reset, but the next time I shutdown and reboot, same issue of blank screen.

-I obviously remove all peripherals, check with a different AC adapter
-Booting in safe-mode does the same problem
-Booting in single-user-mode, then reboot or perform a FSCK does not help
-Booting from OS X DVD, then perform Disk Utility find no problem on disk or permissions
-Reseting the PRAM and NVRAM does not help either (http://docs.info.apple.com/article.html?artnum=2238)

I tried all the standard troubleshooting tips from Apple Support Powerbook. (http://docs.info.apple.com/article.html?artnum=106464#symp3)

Please help.

Powerbook Ti G4, Mac OS X (10.4.7)
  • brun Level 1 Level 1 (0 points)
    I also swap my hard drive with my old one and reinstall from scratch OS X 10.4. Same problem.

    Also, I tried install the Factory DVDs containing all the original software incluing OS 9. I get the message when I boot with the DVD that :

    "The Built-in memory test has detected a problem with cache memory. Please contact a service technician for assistance."
  • tjk Level 7 Level 7 (24,180 points)
    Hi brun,

    Unfortunately, cache is soldered onto the logic board and cannot be replaced. The fix is to replace the LB, which is relatively expsensive. If I were you, I'd probably continue to use it as is, never shutting down, and resetting the PMU if you do have to shut down. Without the L2 cache, you may notice a slowdown in performance, so you'll have to decide if it's worth the money to replace the LB, buy a new PB, or use this one as is. Good luck.
  • brun Level 1 Level 1 (0 points)
    Tks for the quick reply.

    I put the good hard drive in, try to clean any dust in there near the cpu and stuff. Removed then placed back the rams.

    At some point I had this: I checked System Profiler, under memory my two dimms are good. However, under Diagnostic, I also get a note that the result failed and the type is external cache. Also, OS X is starting to struggle to resync the date that I basically reset to Dec 31 1969. Same kind of issue at startup.

    Later on, after a bunch of restart and shutdown, the Diagnostic could not find anything wrong. The PowerBook seems to start even after a shutdown, without a system reset, although I see that it is really looking for the OS as it shows a question mark folder icon. It finally, after 1 sec, finds it and start. I redid a Hardware Test using the factory DVD and as before, all elements PASSED, including Memory and Logic Board. Even the OS 9 Factory DVDs would install if I chose to as it does not tell me that there is a problem with cache memory like it did before.

    I was just using it... at some point, when I was doing more intense task, it froze again. However, it reboots this time without a hardware reset. Then again, another time, froze but I had to reset the hardware to reboot.

    This is strange, not consistent.

    Powerbook Ti G4 Mac OS X (10.4.7)
  • eww Level 9 Level 9 (52,975 points)
    If a cache failure is detected sometimes but not always, you can safely conclude that the cache is far enough gone to worry about, even though its problems are (at least for now) only intermittent. If it interferes with your work, you'll need to replace the logic board, as tjk has written above, to make the computer run normally again. Whether or not that's worth doing is a decision you'll have to make.
  • brun Level 1 Level 1 (0 points)
    Tks for your advices.

    The only thing still bothering me, other than the fact that I will have to shell a lot of money on a new portable, why is it that the powerbook can still function ok? It has been one day since I have not restarted or shutdown. As long as I don't do to much at the same time, things are running ok. I fixed my date to avoid some crazy things going on with iCal. Sometimes, a simple things like extracting a .SIT can take a long time, which is abnormal. L2 cache is what is my external cache memory? Why is it that it can still function? Are things risking to go downhill from now one, including a major short circuit at some point? Tks.
  • eww Level 9 Level 9 (52,975 points)
    The function of the cache is to speed things up, by making whatever code is likely to be needed next available more quickly than if it had to be read from the hard drive. Cache is mostly not essential. I suspect yours only brings your computer to its knees because one moment it's working — so the OS feeds data to it — and the next moment it isn't, so when the OS reaches for what's supposed to be cached, it's not available. My guess is that if your cache never worked at all, your computer would be slow but more reliable.
  • brun Level 1 Level 1 (0 points)
    Where can I find information regarding the location of the external cache? I doubt I can find a new board or processor cheap, perhaps from a powerbook like mine that died from another cause (busted screen, hinges, etc...)

    I think I have the powerbook G4 release prior to the gbit version, since I bought in in Sept 01. Here is what I found on it (http://support.apple.com/specs/powerbook/) :

    Processor and memory
    400- or 500-MHz PowerPC G4 processor with Velocity Engine
    1MB backside level 2 cache on processor module; 200- or 250-MHz dedicated 64-bit backside bus
    100-MHz system bus
    Integrated floating-point unit and 64K on-chip level 1 cache (32K data and 32K instruction)
    128MB or 256MB of PC100 SDRAM; two SO-DIMM slots support up to 1GB

    Powerbook Ti G4   Mac OS X (10.4.7)  
  • eww Level 9 Level 9 (52,975 points)
    Apple never publishes schematics of its products, and doesn't even train its own technicians in component-level repairs to its circuit boards, which are simply never done. You should forget about trying any such thing. Look on Ebay for a used logic board with a written warranty of serviceability from a vendor with a clean reputation, or cantact any of the following Powerbook parts vendors:

    http://www.pbparts.com (parts and repair work)
    http://www.dttservice.com (parts and repair work)
    http://www.powerbookresq.com (parts and repair work)
    http://www.powerbookmedic.com (parts and repair work)
    http://www.tekserve.com (parts and repair work)
    http://www.ifixit.com (parts and excellent, illustrated online take-apart instructions)

    Prices for the same parts vary WIDELY, so check around.
  • brun Level 1 Level 1 (0 points)
    It is funny. If you call Apple directly, they tell you thet are only able to help you on the software side. For hardware, you have to go to an authorized service dealer, which asks to bring the laptop in to check it, when they could eye ball the problem based on symptoms you tell them, from rigorous do it yourself troubleshooting.

    Tks for the link. So if I understand correctly, the logic board contains an all in one (video cards, motherboards, I/O, processor, etc...). You break it, you change it all. In my case it would be a 300$ part. If I take into account that my battery does not even last 1 min since two years ago, It is perhaps time to use it moderatly and start thinking about a 1500$ MacBook which is so much faster, even with the not so great graphic card from Intel. Since you mentioned in another post that you cannot disable the external memory cache in powerbook G4, I can only hope it stays at Failed so that I don't get crash freeze. It is slower than usual for sure. I will see how patient I am. I keep my pbook on at all time, on sleep mode and restart. That way, my clock stays ok and I can reboot. A shutdown will require most of the time a logic board reset. Tks for the help.

    Powerbook Ti G4   Mac OS X (10.4.7)  
  • tjk Level 7 Level 7 (24,180 points)
    So if I understand correctly, the logic board contains an all in one (video cards, motherboards, I/O, processor, etc...). You break it, you change it all.

    Correct.
  • eww Level 9 Level 9 (52,975 points)
    For hardware, you have to go to an authorized service dealer, which asks to bring the laptop in to check it, when they could eye ball the problem based on symptoms you tell them, from rigorous do it yourself troubleshooting.


    That's right, and it isn't surprising. Even quite a competent do-it-yourself troubleshooter can't be relied upon to think of everything that might be important to tell someone over the phone about the computer, its usage, its surroundings and peripherals, its history, etc. And for a technician on the phone to walk a non-technician through the service manual's diagnostic procedures would take as long or longer than doing it in the shop, but it wouldn't be paid for. So Apple insists on testing your hardware themselves instead of holding your hand while you do it. Pretty understandable, I think.
  • brun Level 1 Level 1 (0 points)
    Since my last post and successful restart to use the PowerBook on life support, I have not shut down the Mac. I only restarted and used sleep mode to keep power on the logic board component.

    I know for a fact that my L3 Cache is not working anymore. Replacing it means a new logic board, so I bought a new mac. I still want to keep this baby alive.

    So the solution is to to a simple reset of the Power Management Unit (PMU). The step by steps are explanined here:
    http://support.apple.com/kb/HT1431#faq8

    After reseting, the OS boots but is totally lost with a computer clock set at March 14th 2001. A quick setup in the Preferences to set it up manually and a restart, then no shut down keeps the PowerBook alive. Auto setting the time does not seem to work.

    *My question is there a real link between L2 Cache and PMU?

    *Would changing the button cell battery on the logic board avoid the PMU issue?
  • brun Level 1 Level 1 (0 points)
    Something is wrong on the logic board. Nothing worth repair when you can get better new.
    I simply press the Resest button behind the powerbook and it start again. It does not always loses the clock time.