When You Need to Memtest Your RAM

My Powerbook recently suffered a mild health crisis. It started when I woke it from sleep one morning and it immediately gave me a kernel panic. I rebooted and got another immediate kernel panic, at which point I sighed and thought, "Here we go..." I actually thought I fixed the problem by reseating the RAM, since the kernel panic plastered a bunch of helpful text across my screen saying something about "illegal memory instruction." But alas it was only a short-lived fix as the kernel panics returned soon after.

It turned out the lower RAM slot was dying, and in fact it finally died permanently later that day and now the Powerbook was only reading 512 MB of memory (the upper slot). Dead lower memory slots were a common problem in aluminum Powerbooks, though Apple's AppleCare extension program for this model is long past. I could either re-solder the slot joints back in place or replace the entire logic board. Since I don't have soldering skills handy, replacing the logic board it was!

Fortunately I have a spare, identical Powerbook for just such an occasion. For awhile, I've wanted to take apart both Powerbooks and combine the best parts from each, so events provided the impetus. After much surgery (basically moving the hard drive, trackpad case, and LCD display to the spare which had a good bottom case and logic board), the patient came out more-or-less intact. I used these iFixIt tutorials, which I can't recommend enough. If any of you want to do something like this, let me offer a tip. When following the tutorials, always refer back to each step one-by-one, even if you've done it a few times before and think you have the hang of it. Because eventually you'll overlook a step and wonder why the trackpad case won't pull off the left side even though you're bending it out of shape and then you realize you forgot to take that side's screws out. Now, I didn't do this myself, of course. That would make me the stupidest person on the planet. I'm merely writing to enlighten you, dear reader.

Unfortunately this wasn't the end of my adventures. I also ordered a pair of one gig RAM DIMMs to max out my memory. I'm starting a family photo scanning project and I'll be working with some very large picture files. So naturally I installed the new RAM and got a kernel panic. Then I rebooted and the System Profiler's diagnostics showed the bottom slot failed and was only reading 512 MB. At this point I'm thinking this isn't my lucky week. After reseating the RAM, everything seemed to work until more kernel panics returned. At this point it was finally time to test the RAM (when Darth Vader targets me in his cross hairs, he says, "The ennui is strong in this one.").

To test, you need a unix program called memtest. An installer is available for download at Command-Tab, which installs the executable into your /usr/local/bin. Version 4.22 supports both PowerPC and Intel. Once you have it, you can reboot into single user mode (command-s at the chime) and run the command "memtest all 2". Over the next couple of hours you'll see either a bunch of "ok"s or a bunch of failures. I saw failures. The good news is the seller agreed to give me a refund almost instantly after I sent a request.

Memtest is also bundled with Applejack, another troubleshooting utility that runs in single user mode. I saw other sites trying to sell memtest for a fee, but it's freeware so I don't know what that's about.

I'll try my luck with new RAM again, but right now I'm glad to have two functioning slots even if they're housing my old 512 MB DIMMs. Finally on the subject of scanning, check out these posts at Quadras, Cubes, and G5s about digital photography and scanning on a 7300. Very interesting.