What is this Powerbook's problem?
October 17, 2008 3:23 AM   Subscribe

What is this Powerbook's problem? Rare kernel panics followed by disk catalog errors on startup, but I've ruled out the HD and OS.

15" Aluminum Powerbook, 1.5GHz, OS X 10.5.5.

It all began when, in the course of trying to get it to stop undercharging the battery, I did a PMU reset. On the first post-reset restart, the disk gave all appearances of crashing -- got about 10 seconds into the startup and then froze, and then couldn't be booted afterwards. I booted from disc and installed a new OS, which also would have occasional panics after/during restarts, and once it just had a system-wide freeze in the middle of otherwise working, which didn't even show the kernel panic multilingual announcement (ugh, even typing that I'm thinking "you know it's the logic board", but read on please).

Apple Hardware Test checked everything out as being OK, and after repairing the post-panic HD, Disk Utility also gave the HD a clean bill of health as far as that goes.

I originally felt that the HD was the most likely culprit here (it's old and mechanical, while the other two likely possibilities -- the RAM and logic board -- are solid state and don't have such an obvious reason to up and die after four years of working) so I put in a new drive. Symptoms haven't changed: sometimes restarts go wrong, followed by catalog errors on the drive when I run fsck in single-user mode. The catalog errors can be repaired in single-user mode. Since the kernel panics are sort of rare, I don't feel like I can easily test the RAM sticks with the "take one out, see if things are better" method, although I am certainly wondering about them now.

The practical issue is that every time it does happen and the catalog is repaired, Time Machine no longer recognizes the things it's backed up already and attempts to back up the entire drive again, making it useless as an incremental backup tool, and the combination of weird computer + no incremental backups is no good.

What do you think, definitely the logic board? If so, that is going to be the end of the line for this Powerbook. Or would you proceed by replacing the RAM (it isn't very expensive, but on the other hand I don't want to waste the money on it if it isn't to blame).

Any suggestions? Keeping in mind that I've already run Apple Hardware Test and it reported no problems, and there is a brand-new HD and a brand-new OS install, and both the PMU and PRAM have been reset in the course of recent events.

posted by Your Time Machine Sucks to Technology (6 answers total) 1 user marked this as a favorite
My guess is that your PowerBook is likely showing the first signs of the well-known lower RAM slot problem with this model PowerBook. You should remove the RAM from the lower slot for a day or two to see if the Kernel Panics stop.
posted by mrbarrett.com at 4:55 AM on October 17, 2008 [1 favorite]

Go download and install Memtest OSX. Follow the included directions to test your ram.
posted by Wild_Eep at 5:41 AM on October 17, 2008

You know, I think you just nailed it. It is actually from the previous generation of Aluminum Powerbooks, but to all appearances after googling "powerbook lower ram slot", they also had the same problem.

Although I had previously checked the RAM info repeatedly and there was nothing strange there, after reading your link I checked out System Profiler yet again and noticed that today, one of the sticks was reporting only being 256MB instead of 512MB. I labeled the sticks 1 and 2, and tried putting each one separately in the two positions, and stick 1 caused a kernel panic on startup in both positions (upper and lower). However, since both sticks had checked out as fine only a week ago with the AHT and they both used to report as the correct size, my guess is that the stick that was in the lower position (that was stick 1) was gradually harmed by the lower RAM slot flaw and was not actually where the problem originated.

I pulled the bad stick and made sure the remaining stick was in the upper slot, and I'm optimistic. Mrs. YTMS says she doesn't need to have it replaced with a 1024MB stick, but we'll see if she still feels that way after using Leopard with 512MB of RAM for a while! Thank you for the timely solution/mental nudge, mrbarrett.com.
posted by Your Time Machine Sucks at 5:41 AM on October 17, 2008

Is Memtest better than AHT?
posted by Your Time Machine Sucks at 5:43 AM on October 17, 2008

All RAM tests are seriously flawed. Ive seen ram tests pass on known bad ram that would bluescreen a computer in 10 seconds. I think theyre next to useless as diagnostic tools. If you have to use one then use at least 2 different ones and let it run at least overnight.
posted by damn dirty ape at 3:01 PM on October 17, 2008

What you could also do is install Applejack (and the optional install of memtest) and run the mem test from that. I LOVE applejack, esp now since it can run in 10.5

BUt yea, it def sounds like the lower ram slot of doom problem.
posted by ShawnString at 4:41 AM on October 18, 2008

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