Freezing G5 Quad: Maybe it’s not the RAM

Posted by Pierre Igot in: Macintosh
September 5th, 2006 • 11:38 am

Here’s the latest instalment of my latest hardware saga involving a Power Mac G5 Quad bought in November 2005 that started freezing on a more or less daily basis some time in August 2006.

As indicated in my previous posts on the topic, I was able to quickly eliminate USB and FireWire peripherals as potential culprits. Once that was done, I started suspecting my RAM modules. As far as I know, RAM modules can become defective after having worked without any problems for months or even years. It might be unusual, but it’s not unheard of.

So I tried to determine which RAM module might be defective. The G5 Quad came with 2×256 MB of RAM, and I added 4×1 GB of third-party RAM to it when I bought it back in November 2005. (I didn’t have any problems with frequent freezes or kernel panics until August 2006.) The RAM modules have to be installed in pairs in the G5 Quad, so the testing was a bit more challenging than it might have been on another model.

Here is what I have been able to establish.

  1. I have twice run the G5 Quad with only the 2×256 MB of RAM that came with it for extended periods (several days) without experiencing any freezes.
  2. I have run three lengthy passes of the third-party utility memtest in single-user mode with three of the four 1 GB modules installed (with modules 3 and 4, and with modules 1 and 3), and in both cases the RAM modules passed the tests with flying colours. I have yet to run the tests with module 2 installed in one of the slots, but at this point I strongly suspect that it would show that the RAM is just fine. (See why in the next bullet.)
  3. I have used the G5 Quad with 2.5 GB of RAM using all six possible combinations of 2×1 GB modules in addition to the 2×256 MB of RAM. In other words, I used the G5 Quad with modules 1 and 2, 3 and 4, 1 and 3, 2 and 3, 2 and 4, and 1 and 4. In all cases, I have ended up experiencing either a freeze or a kernel panic within more or less 48 hours, sometimes significantly less.

The only conclusion that I can reach after this is that there is a strong possibility that the 4×1 GB third-party RAM modules are not defective. After all, if the RAM was the culprit, to explain the situation described above, I would have to assume that three of the four 1 GB RAM modules have become defective at the same time—yet that the defects are not serious enough to show up during memtest’s battery of tests.

It is a rather unlikely explanation. Of course, the freezes do not occur with only the 2×256 MB of RAM (unless I have not waited long enough), so obviously the presence of the extra third-party RAM is a contributing factor. But that doesn’t prove conclusively that the third-party RAM itself is the problem.

Betalogue reader ssp was right to point out the problems that many people experienced with the late 2005 iBook G4 laptops. These people didn’t experience kernel panics or freezes, but there was a serious degradation in their laptop’s performance only when they had more than 1 GB of RAM in their machines. The problem turned out to be a bug in the AirPort software and was eventually fixed, but the important thing here is that it was a problem that only occurred above a certain threshold of RAM amount. So the RAM was a contributing factor without being the cause of the problem.

At this point, I am not quite sure what to do. Since I can connect the G5 Quad to my LAN via Ethernet instead of using the AirPort connection, I have tried turning AirPort off altogether on the G5 Quad, in case the problem has anything to do with AirPort. But I am not too optimistic… It’s been 24 hours and I wouldn’t be surprised if I get a freeze or a kernel panic in the next 48 hours or so.

If I do, then I guess the only option I will have is to get back on the phone with Apple and explain the situation. What I do know is that

  • there is nothing wrong with the operating system or the software I use (since the G5 Quad runs fine, albeit slowly, with only 512 MB of RAM)
  • there is nothing wrong with my USB and FireWire peripherals (since I got a freeze even with all peripherals disconnected except for my mouse and keyboard)
  • the freezes and kernel panics only occur when I have some extra RAM installed
  • there is nothing that proves conclusively that there is a problem with the third-party RAM.

I do not particularly fancy spending another $700 or so on more third-party RAM modules just to make sure that I would still get the freezes with another batch of third-party RAM. (I doubt very much that Apple would provide me with two “certified” RAM modules just to eliminate that possibility for sure.)

I don’t really see how I can contact the company that sold me the third-party RAM and tell them that it is defective and needs to be replaced. They are never going to believe that three or four modules have become defective at the same time. And I suspect that they might use memtest to test the RAM modules themselves and find that nothing appears to be wrong with them.

Unless switching off AirPort cures the problem and enables me to designate a faulty AirPort card as the culprit here, I am afraid the only other possible explanation is some other hardware defect in the G5 Quad itself. Maybe a defective RAM bus? I don’t know enough about the underlying technology. But I do know that there is a good chance that Apple will ask me to bring my G5 Quad to an authorized repair shop to have it tested.

The closest repair shop is a three-hour drive from here. And they are not going to be able to reproduce the problem easily. Like me, they are going to have to leave the machine on for several days, and try various combinations of RAM (possibly with their own “certified” RAM modules).

In all likelihood, this will be a lengthy process and I will be without my machine for an extended period of time. It’s still under warranty, of course (I bought the three year AppleCare warranty anyway), so the problem is not with the money. It is with the huge inconvenience of having to make several six-hour trips to the authorized repair shop and being without the machine for extended periods. (I’d have to go back to my G4 MDD, which I still use as a test machine, I guess. And of course I wouldn’t be able to use my 30″ display with it.)

This is all quite frustrating. And once again the back of my mind there are some rather serious question about the quality of Apple hardware in recent years… First, the unacceptably bad AirPort reception on the PowerBook G4. Then the horrendous noise issues with the G4 MDD. Then the traumatizing experience with the mooing MacBook. And now this?

Maybe I am just unlucky. Maybe my house is jinxed.

Or maybe Apple’s hardware is just not what it used to be.

13 Responses to “Freezing G5 Quad: Maybe it’s not the RAM”

  1. Kernel Panics and more « Bloody Fingers says:

    […] I’ve been trying to test the new 3ivx crush application these last few days (as Zav was kind enough to send me a free license) but I’ve been having trouble with my computer, in the form of numerous Kernel Panics. The Kernel Panics happen every 15 minutes to 2 hours, during interactions with the user (hint ?), either in Safari, Word, Transmission, whatever. When I’m not interacting with the computer (e.g. watching or encoding a movie, listening to music), things seem to run fine, but I’m not sure. At other times, running applications start to hang one after the other until the whole system is hosed, or the fans suddenly decide to turn on full blast. Trying to put the Mac to sleep is a sure way to produce these two effects one after the other. All these fuckups are seriously damaging my cool. Knowing I’m not the only one is not comforting. […]

  2. Paul Ingraham says:

    You’re starting to get as paranoid as I am, Pierre! Of course, I really do live in a vortex of bugginess, and as you know, “You aren’t paranoid if they’re really after you.” Anyway, my minor and not especially helpful point is just that I don’t know that it’s ever been any different. As you know, I am among the first of your readers to agree that Apple’s standards seem to be drooping, their priorities veering off in the direction of fashion over function, but I tend to think that applies more to software design than to hardware. Seems to me the hardware has always had issues, right back to the first Macs. Has there ever been a Mac without quirks? Or, to speak a little more precisely, has there ever been a Mac product line-up without at least one flaky member? Certainly some Macs have been fairly excellent pieces of hardware, some of the best computers ever made, but — I submit — there have always been a few with problems.

  3. Pierre Igot says:

    It’s true that all generations of Macs have had their problems. The issue here is that I have had all these problems affect my machines since 2001. Statistically, it’s just not very likely that I would get trouble-free hardware for 15 years and then start getting troublesome hardware with every new machine that I buy after 2001. So I cannot help but think that there is a more general trend here. Of course, I have no hard proof of it, but you’ve got to admit that it’s troubling.

  4. ssp says:

    I’m with Pierre on this one… remembering the Macs we had in our family: Starting with an LC III and Centris 650 which work without problems until today. Then at my civil service we used a Quadra 950 and Performa 630 without problems (although I heard that something in the Quadra had to be replaced after 7 years or so). At home we moved on to a Power Mac 8200, 7200, 7300, 4400. Just the first had a tiny problem (the serial port not working properly after a year) – for which a local Mac dealer gave me a free replacement battery (strange problem…) within minutes of mentioning it. Similarly the Pismo Powerbook kicked butt and is still doing so on a daily basis (just one crack appeared in the case after some years).

    The only Apple product giving me serious trouble in the old days was the notorious AppleVision 1710 display. I had it exchanged twice, the geometry never became reasonably good and it just broke after five years or so.

    Compare that to my PowerBook G4 Titanium (flickering screen, broken at headphone socket, broken screen hinge, exitus), my dad’s PowerBook G4 Aluminium (ugly, battery replacement), my iBook G4 (charger replacement). My MacBook also starts to have a flickering screen.

    And on my friends’ desks it’s not looking better. Plenty of replaced batteries there, at least one new hard drive, two new iBook logic boards and so on.

  5. matsw says:

    The problem here is lack of scientific method. Test the reamaining RAM module with memtest and then we can talk.

  6. Pierre Igot says:

    matsw: Even if I test the remaining RAM module, that won’t account for the fact that the G5 is still freezing when only two of the already-tested modules are installed. So I don’t really see the point. If we are going to talk about a scientific method, let’s use basic common sense too.

  7. danridley says:

    Have you tried all four 1 GB modules *without* the original RAM? Sometimes (not often, but sometimes) you get weird issues with mismatched RAM, even if all the RAM is good.

    Do you have access to a PC that will accept your RAM? If so, try testing it with MemTest86+ ( This is a more modern and comprehensive RAM test suite than memtestosx, which is based on MemTester.

  8. Pierre Igot says:

    Dan: Thanks for your suggestions. I might try without the original RAM, if all else fails. But it would be strange that the problems would only start after 9 months of perfectly normal operation.

    I don’t have access to a PC. However, I do have a colleague who also has a G5 Quad, and also has 4 x 1 GB of RAM. She’s offered to let me borrow 2 of her modules to test them on my machine to see if I still get freezes with them. (She’s not getting any freezes.) Of course, if there’s some weird electronic voodoo that might damage her RAM (not too likely, I don’t think), I’d have to replace them, but it’d be better than to have to purchase new RAM myself.

    BUT—big but—I’ve been running the G5 Quad without AirPort for three days now and haven’t had a single freeze. Still too early to tell, but maybe we are onto something here.

  9. danridley says:

    Or maybe Apple’s hardware is just not what it used to be.

    Oh, I miss the days of the PowerBook 5300 — now that was the way to run a battery recall. Or the Performa 600 — even back then, nobody could cripple a system with a poor bus design like Apple.

    Point being, Apple (and all the other computer makers) have had their lemons all along, and none of the problems of the last few years even compare to the issues the whole industry had to deal with a decade ago.

    In my book, there are only a handful of systems that Apple has had near-perfect engineering and delivery on: the SE/30, the IIfx, the Wallstreet and Pismo, the late-2001 iBook G3, the iMac G5 and iMac Intel. Everything else has had its weaknesses and quirks, and that’s been true since the 80s.

    Problems get more press now with blogs and the like, but I think there’s another aspect to it as well. The Performa 600 was a mess: I personally know of CD-ROM drives falling into the case, an unusual number of SCSI controller problems, RAM issues, and video quirks. But nowadays, we’re a lot less likely to see bad chips: manufacturers in general are a lot better at testing for things like that. And we’re a lot less likely to see defects in assembly; again, better QC and procedures. So where in the 90s, you and I and three of our friends might have gotten bad Performas, they’d be more likely to have a bunch of different problems; where now, most buyers are happy with their MacBooks, but the ones who aren’t are all having the same few problems.

  10. Pierre Igot says:

    I don’t know. In the absence of wide-ranging scientific surveys, all we really have is our own personal experiences and media/on-line reports. It’s obviously hard to get a clear picture.

    All I can say is that I didn’t have any major hardware problems with my own machines until 2001. I have personally owned a Mac Plus, a Mac SE, a Mac IIsi, a Power Mac 7100, a Power Mac 8600, and a Power Mac G4/450. The problems started with the PowerBook G4. Every machine that I have personally bought since then (PowerBook G4, Power Mac G4 MDD, MacBook, and G5 Quad) has had at least one major hardware problem.

  11. ButchAnton says:

    Pierre, I’d love an update. I have a Quad in the same configuration as yours, and I see at least one kernel panic a day (three today). Please do let us know if using wireless ends up being the culprit, or if you find another solution.


  12. Pierre Igot says:

    I will post a complete update (in a new post) as soon as I have something tangible. Right now, things are still in a state of flux. All I can say is that AirPort didn’t appear to be the culprit.

  13. Pierre Igot says:

    ButchAnton: Please see this post:

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