Running Tiger on a G5 Quad with 512 MB of RAM: Atrociously painful

Posted by Pierre Igot in: Macintosh
August 21st, 2006 • 10:24 am

I seem to have developed a bad case of faulty RAM.

It started on Friday with a system freeze while I was working at the computer. I thought little of it—after all, while freezes are fairly uncommon in Mac OS X, they have been known to happen from time to time. My system had been very stable in recent months, and I had little reason to worry. I just did a hard reset and got back to work.

Then on Saturday, I was away from the computer most of the day, but it was on and running, slowly completing some downloads over my painfully slow dial-up connection. While I was in another part of the house, I heard a pretty loud noise coming from the office. I went to see what it was about, and realized that my G5 Quad was on with all its fans running at full speed. It was a pretty noisy racket.

I tried to wake the monitors from sleep by pressing a key on the keyboard, but nothing happened. The computer was obviously frozen in that very loud state. I did another hard reset and waited for a few minutes before booting up. After that, everything seemed fine and I left the machine running in the office for the rest of the afternoon.

In the evening, the same thing happened again. While I was away from the office, all the fans came on again and the computer was again in that same frozen state, requiring a hard reset.

At this point, I was starting to worry. I had read about power supply failures, leaks of liquid coolant, etc. so I opened up the machine and checked to make sure that everything seemed OK inside. There were no leaks and no funky smells coming from any part of the machine, and nothing seemed to be abnormally hot. There was some dust, so I cleaned up a bit, and put the machine back together and booted again.

Once again, things appeared to be fine. I left the machine running during the night, with the office door closed, but woke up at 5 am, again hearing the loud fan noise through the door. I went in and saw that the problem was the same again. This time I just turned the machine off altogether and went back to sleep.

On Sunday, I went through some basic steps, such as resetting the PRAM, to try and see if it would make any difference. But I also had some work to do on the machine, so after I reset the PRAM, I just booted the machine and started working. Within a couple of hours, I got another system freeze.

Before going to the next troubleshooting phase, I thought I’d call AppleCare just in case it was a known problem of some kind with these machines and I could save some time. The AppleCare technicians said that the next step was to eliminate all USB and FireWire peripherals and see if the problem occurred again. He also explained that, when the machine freezes, after a while all the fans kick in automatically as a precautionary measure and stay on until the machine is reset. So obviously what was happening while I was away from the machine (the loud fans and frozen machine) and what was happening while I was working with the machine was the same thing: the computer was freezing, and then the fans kicked in after a while if the machine was left unattended.

I eliminated all peripherals except for the keyboard and mouse, and went back to work. The machine froze again within a couple of hours, so that eliminated the peripherals as the culprit. I didn’t get back on the phone with AppleCare. I knew what the next step would be: Check the third-party RAM.

In addition to the 512 MB that came with the G5 Quad, I have 4 modules of 1 GB each in the G5. So I took all 4 modules out and started using the G5 Quad with only the 512 MB of RAM that came with it.

My, this is a painful computing experience! I just cannot believe how slow the machine becomes with only 512 MB. There was, quite predictably, lots of hard disk activity, but I didn’t expect the machine to become this slow. It was actually quite close to being unusable. Everything, absolutely everything was excruciatingly sluggish.

It was actually easily much worse than using Tiger on my PowerBook G4 (Titanium), which has only ever had 384 MB of RAM, and whose hard drive must surely be much slower than the hard drives that I have inside my G5 Quad. Tiger is slow on that PowerBook, but it’s still usable.

So, why such a big difference? It is true that I have many more things running at the same time on the G5 than I have on the PowerBook. I have a number of utilities and applications open. But I thought that, when an application wasn’t in use for a while, Mac OS X could easily reclaim its RAM for other applications… While this is obviously what Mac OS X does, as can easily be construed from the amount of hard disk activity when switching applications, I was quite surprised to see that even the foreground application could easily become barely usable.

My suspicion is that it might have to do with the size of the screens I am using with this G5 Quad. I have a dual-monitor setup with a 30″ display as the main screen and a 23″ display as the secondary screen. The Mac obviously relies on the memory of its video card to support this dual-monitor setup, but the video card is just one part of the equation. This is still a lot of screen real estate for the operating system itself to handle, and the complex layering calculations involved when there are quite a few windows open still require a fair amount of regular RAM, I suspect.

I was still quite surprised at how painfully slow the whole system was. It was really like trying to use Mac OS X 10.2 on an old bondi-blue iMac with 64 MB of RAM (which I have tried). Not impossible, but incredibly painful. I find it a bit hard to believe that, with so much more processing power, with a much faster video card, and with much faster internal hard drives, the G5 Quad couldn’t provide me with better performance than the PowerBook G4 with its paltry 384 MB of RAM, slow hard drive, and lousy video card—and was actually significantly worse in many situations.

Fortunately, within 24 hours I was indeed able to determine with relative certainty that the problem is with my third-party RAM modules. Using the G5 Quad with 512 MB of RAM might have been painfully slow, but I didn’t get a single freeze, and the machine went through the whole night without any trouble.

So this morning I installed a pair of 1 GB modules back in. Unfortunately, they have to be installed in pairs, which will make the process of identifying the faulty module—assuming there is only one of them—a bit more complicated. But I can tell you that running Tiger on a G5 Quad with 2.5 GB of RAM instead of 512 MB makes a huge difference!

So now I am waiting for the next freeze. If it doesn’t occur within the next 48 hours, it’ll be time to install the other two modules and see what happens.

8 Responses to “Running Tiger on a G5 Quad with 512 MB of RAM: Atrociously painful”

  1. Simanek says:

    I have Panther running on an original iMac with 128MB of RAM and a Lombard PowerBook with 512MB of RAM. The iMac is a bit painful but fine for surfing the web on dial-up. The PowerBook is really fairly decent if you stay away from YouTube. Just thought I’d throw this out there. I think Panther is an excellent OS. Apple had finally worked out many of the kinks and it still remained reasonably lean on hardware demands. I would hate to see what Tiger would do to the iMac (yes, I realize it’s not supported hardware for even 10.3). I just started working on 10.4 at work with a dual 2GHz G5 and I have to say that, aside from it’s improved native interaction with Windows networks, I am not impressed. It’s even slower than the same hardware running Panther in certain network file situations. I’d be curious to hear your perspective on Tiger compared to its predecessor.

  2. Simanek says:

    And sorry to hear about your RAM. That sucks, but I’m sure you were fearing something far worse.

  3. matsw says:

    Testing RAM this way is crazy. It is very time consuming and can lead to a bad filesystem: think that eveything written to disk goes through a buffer in RAM. If the data in the buffer is corrupt, so is the data on disk. Go to and get memtest. I had a faulty RAM module once and it was diagnosed in seconds. I am not sure memtest will tell you which module is at fault, but it will identify a RAM problem much quicker than waiting for a crash to happen, and your testing time will be much shorter.

  4. Pierre Igot says:

    Simanek: I am definitely relieved that the problem appears to be “only” with the third-party RAM and not with the G5 itself. While the RAM situation is annoying, at least it’s something that I can fix myself and I don’t have to take my machine to the local repair shop, which is a 6-hour round trip!

    10.4 definitely didn’t bring any substantial performance improvements over 10.3. But it is not vastly slower than 10.3 on the PowerBook G4 Titanium with a 400 MHz processor and 384 MB of RAM. It’s still usable. I am of course disappointed that 10.4 didn’t continue the trend of further performance improvements over its predecessors, but I can also understand that the addition of new features such as Spotlight requires additional resources.

    matsw: Thanks for the link. My computer froze during the night with the 2 GB that I had put back yesterday, so I switched to the other 2 1 GB modules. I ran memtest on these two modules this morning. It’s a very long process! (Took all morning, basically.) But after three passes it says everything is OK with these two modules, so we’ll see if the computer is stable in the next few days.

    I realize that living with faulty RAM can be somewhat dangerous, but I don’t think the risk is that great. My impression is that the faulty memory can cause a freeze at any point, and it would have to occur at very specific points to actually cause damage to the file system, wouldn’t it? The likelihood of this is not very high.

  5. matsw says:

    Note that it is often not necessary to run all memtest’s tests to discover faulty RAM. When I had it, one of the first tests identified it in minutes.

  6. Pierre Igot says:

    Right, but if the RAM is not defective, you have to go through all the tests to make sure :).

  7. danridley says:

    Faulty RAM can cause silent corruption of data files. If you save a file, and the version of that file in RAM has a few flipped bits because of faulty RAM, that corruption gets passed into the copy you just wrote to disk. No, it’s not likely, but it can be insidious, and it might not be visible — some strange behavior in a particular file that you don’t discover until months down the road might be traceable back to bad RAM.

    And you’re right, dual-monitor Tiger in 512 MB is awful. I’m actually still somewhat RAM-starved on my MacBook with 2 GB, and I’m hoping the system will support 4 GB once the 2GB SO-DIMMs get cheap enough to consider.

  8. Pierre Igot says:

    Dan: Yes, I can see that, and I definitely don’t want to live with faulty RAM more than the minimum necessary. I suppose it’s possible that my RAM has been faulty for a while, so I don’t suspect that a few more days will make a huge difference. But it’s a concern, obviously.

    That said, I seem to have identified the pair that contains the faulty module. (I have the other pair in right now, and I am not getting any freezes.) So there’ll only be a few more days of testing to determine which of the two modules is the faulty one.

    Tiger with 2.5 GB of RAM on the G5 Quad with the two monitors is fine… But I suppose we all have different needs when it comes to RAM.

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