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RAM slot(s) failing in some PowerBooks (#2)
We continue coverage of an issue where the lower (or less frequently, upper) memory slots in some PowerBooks fail, leaving users with less available RAM than is actually installed. As previously noted, some users are not aware of the issue until they check the "About This Mac" pane accessible via the Apple menu or experience significant slow-down in a particular application.
It now appears that there are two causes, and two very different solutions to most cases of this issue.
In one case, the RAM is simply seated improperly. Removing the module, and re-installing it, making sure the connection is tight, has resulted in the previously disabled module working again for several readers.
MacFixIt reader David Schloss, for instance, writes:
"After reading your posts on the failing RAM in some PowerBook models, I checked my 'About This Mac' and found that my PowerBook 15" 1.25 GHz was showing 1GB instead of 2GB of RAM available. I don't have the test CD handy so I powered it down, took out the upper DIMM and tried to power it up. I got the 'error' noise associated with bad RAM. I flipped the same DIMM to the upper slot and it booted. I then powered down, and put the DIMM back into the lower slot, same issue. Took it out and re-seated it and this time it started up fine. I put back in the second DIMM and the Mac sees both. I'll keep running it until I get to a copy of the test CD, and I'll email my results."
In the second case, the PowerBook's logic board is faulty, and must be replaced. Most users whose machines are still under warranty have reported success in seeking repairs from Apple.
Swapping RAM modules A handful of users have been able to successfully work around this issue by simply switching the the location of their RAM modules (module in upper slot moved to lower slot and vice versa).MacFixIt reader Davis Chapman writes:
"We have a Titanium PowerBook G4 17-inch 1 GHz which just got back from the shop with a RAM slot failure. At first the machine would periodically crash. Then we noticed that sometimes it reported only 256 MB in the second slot rather than 512 MB. Switching the third party ram into the primary slot worsened the problem and we finally need the logic board replaced as well as both RAM modules. Thank goodness we had AppleCare which took care of the logic board and Apple's RAM module."
Another reader, James Franklin writes:
"I just received my 15" Rev B PowerBook back from repair a couple days ago for just this problem. RAM installed in the lower slot just disappeared. Fix was to replace the main logic board. Even though my Powerbook was out of warranty (by 3 weeks), Apple fixed it at no charge."
Unfortunately, other readers are having difficulty obtaining service from Apple, with technical support representatives blaming the problem on "bad RAM" --- which may be a causal factor in some instances of this issue, but not all.
One reader having difficulty getting repairs, Jurgen Proschinger, writes:
"Now that my RAM has disappeared and I?ve identified the error you reported using Apple's Hardware Test that came on the installation CD (Apple Care staff recommended ?reinstalling the system,? as usual, which I did of course, not) I?m stuck with the working RAM in the upper slot. When asking Apple here in Germany how long it would take to fix my 15 month-old Powerbook G4 15?? (thanks God I have Apple Care!) they told me that repairs would take a ?minimum of three weeks.? And before that I?m not entitled to get a replacement from Apple. Renting an iBook from a retailer would set me back some EUR 500,- for three weeks, and it?s difficult to find a shop here in Germany that does rent Apple product at all.
"So, for the time being I'm continuing to work with a faulty logic board and less RAM... needless to say, I'm not amused by Apple's customer service nor their response to the problem ('clearly that?s resulting from bad RAM, did you purchase original Apple RAM?')."
Our previous coverage of this issue, in November 2004, revealed a confirmation from one authorized Apple service provider who wrote "I can confirm this issue as I have seen it several times and have had to send units to Apple for this. In some cases the RAM slot fails after a period of initial use and in other cases the slot fails immediately."
Now we've received word from another authorized Apple service provider who provides unconfirmed information about Apple's memory slot testing at the factory:
"My information is that Apple only test the top slot in production to save time. They populate the top slot on the assembly line and if that works, they assume the other slot is OK. False economy. "
Also problematic is the fact that some users are having their logic boards replaced only to have them fail again a few months later.
For instance, MacFixIt reader Jordi writes:
"The same problem occurred with my PowerBooks Aluminum 1.5 Ghz 2004. This is the second time that I've had the problem. They changed my original logic board and the new one had a failed lower RAM slot three months later."
MacFixit reader Hasani Hunter writes:
"I was getting the same problem, with the lower slot no longer being recognized, so I called Apple Support and they suggested that I swap the memory sticks, which I did.. and now everything works fine.. Maybe the act of re-seating the sticks actually fixed the problem (I doubt that it is a permanent one though)."
If you are experiencing a similar problem, please let us know.
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The bad RAM socket problem sounds a little like another problem I've been seeing for a while with some older Macs, such as any G3 or the PCI G4, AGP G4, or Gigabit Ethernet G4: using PC133 RAM in Macs that have a 100 mhz or 66 mhz bus. Though it might seem that this info won't help people with newer Powerbooks, the same basic issue might still apply--RAM vendors may sometimes be selling RAM even to owners of newer Macs, that's rated at the wrong speed for the Mac that it winds up in. With older Macs, PC133 RAM is intended to be run in Macs that have a 133 mhz bus, which is faster than a Mac with a 66 mhz or 100 mhz bus can run it, and so the timing is wrong. When you do this, sometimes the socket the RAM is placed in will see only half the RAM; but whether it sees only half the RAM or all of it, often random crashing occurs. Sometimes a Mac that has a 66 mhz or 100 mhz bus will run OK for two or three years with PC133 RAM, but after a while, it will begin to crash randomly, as the values of the parts inside the RAM board and/or the Mac's logic board begin to drift, causing the timing problem to magnify. I've seen three cases of this in the past two weeks--I replaced the PC133 RAM with PC100 RAM, and all the Mac's crashing problems cleared up.
Many RAM sellers don't know or care about the difference between Macs and PCs--for some time, some of these vendors have been selling PC133 RAM to people with Macs that have 66 mhz and 100 mhz buses, or even selling PC-only RAM and lying to customers, telling them that the RAM will work fine in their Macs. I had this experience with one of the biggest RAM sellers recently--they told a client of mine that PC133 RAM would work fine in any G4, when that's not true. Resellers can reprogram their PC133 RAM boards to run properly at PC100 speed, but some can't be bothered even to do that.
One of the most reliable sources for Mac RAM is Data Memory Systems (800-662-7466, in Salem, New Hampshire). I don?t have any affiliation with them--they just happen to know what RAM should go into a Mac. I haven't had as consistent luck with 18004MEMORY.
Many RAM manufacturers and resellers don't put stickers on their RAM boards to tell you what speed the RAM is, or even its size. This is less of a problem these days--most newer RAM boards, especially those for newer computer models, contain the proper labels--but it's often still a problem. Since Apple System Profiler isn't consistent about telling you the speed of your RAM boards--usually it will report that a PC133 RAM board is a PC100, since that's the speed the logic board is trying to run the RAM board at (but not properly running it)--if you have an older Mac that can boot into OS 9, you can use a utility called DIMM First Aid to tell you a RAM board's specs (DIMM First Aid doesn't run under OS X, even in Classic mode). You can get it from http://www.versiontracker.com/dyn/moreinfo/macos/10415, but if you do a search for it on Versiontracker, it will say it can't be found--apparently they've removed it from their search engine, but its page is still there. You can also find it at www.macupdate.com/info.php/id/5714.
A tray-loading iMac should contain PC66 RAM; slot-loading iMacs through the 17 inch flat-panel iMac running at 1 Ghz should contain PC100 RAM; a G4 PCI, AGP, or Gigabit Ethernet should contain PC100 RAM; and so forth. If your Mac contains the wrong speed RAM, I'd recommend replacing the RAM with the proper speed, even if it seems to be running OK right now--it may not in the near future, and may start acting up at a time when it's not convenient.
You can use the MacTracker utility (available on Versiontracker) to see the bus speed of each Mac model, and thus the speed of the RAM you should be buying for that Mac.
Again, I wouldn't be surprised if some RAM vendors sometimes continue to sell RAM with the wrong specs even to owners of newer computer models. You need to determine the technical specs of the RAM your Mac should contain, then specifically order that RAM, and also find out a way to confirm the actual specs of the RAM boards you're installing, or at least look at the label (if any) on the RAM boards, and compare the specs there to what your Mac should contain.
In reference to jonsaw's analysis of replacement RAM:
My 15" G4 iMac Combo is rated at 100 MHz Bus speed according to System
Profiler. The additional RAM was installed at the supplier in June 2002 for the
'cost of installation'. It is DIMM0/J12: Size:256 MB Type:SDRAM Speed:
PC133-333 and DIMM1/J13: Size:256 MB Type:SDRAM Speed:PC133-333.
Should I expect this will cause problems due to the mismatch?
You might see problems in the future, but there's no way to know for sure. If you begin to have an unusual number of crashes, unexpected quits, hard drive directory damage, etc., you should replace both RAM boards with PC100 speed boards. Many older Macs with 100 mhz bus speeds and whose processor runs faster than 400 mhz, seem to take PC133 RAM boards better, even though the logic board's bus speed is still 100 mhz, and your Mac model's processor runs faster than 400 mhz, so your Mac may be OK, at least for a while. There's no real way to tell except by its behavior. You could run a RAM-testing utility, but I've never found any of them to be worth much, though maybe an OS X utility called Memtest (get it on Versiontracker) might find something, if there's anything to be found. The documentation that accompanies Memtest is typically technoid--it's not a standalone application you launch from the Finder, but rather a command-line utility you launch either from Terminal, or from single-user mode (restart the Mac and quickly hold down Command-S until a prompt appears, then you enter the commands to run Memtest). My boiling down of the simplest way to run Memtest:
Move the Memtest folder to the startup drive's main window, restart the Mac into single user mode (Command-S) so you can free up as much RAM for Memtest to test as possible, then enter:
/memtest/memtest all x
[where x is is the number of passes you want]
If you want Memtest to write a log file to the Mac's hard drive, of the results of the test, you'll need to launch it using Terminal, since Memtest's log file option doesn't work in single user mode. Launch Terminal, and enter
/memtest/memtest all x -l [that's a letter "L", lower case]
This will write the results to a log file in the Memtest folder--good to do in case the Mac crashes, etc. during the test, preventing you from looking at the results displayed onscreen.
To quit before the test is completed, enter Command-Period if you run Memtest while the Mac is running in normal GUI mode, or Control-C if you're running Memtest in single user mode.
Funny you should mention not using 133 speed RAM in a (gigabit) G4. That's
exactly what I bought on purpose. This was widely discussed on forums at
the time when the thought was that the next Macs would require 133MHz
Dimms and the 133's "worked just fine" in the (gigabit) G4. I guess I was
lucky, and per your comment, it did work "just fine" for three years. When the
AppleCare ran out I bought a newer G4 and sold the old, used (gigabit)
model. I wonder where it is now and whether or not it is still running? Very
good post and I appreciate your comments. I generally buy RAM at Ramjet
and they've been very profesional to deal with for about six years. I've
bought a ton of RAM through them for varios clients. They've
even overnighted replacement Dimms for bad ones before they received the
original bad Dimms back. I've heard of the vendor you mention and they
have an excellent reputation. Back when so much 3rd party RAM was failing
as the result of that firmware update a few years ago when the 3rd party RAM
was just a *little* out of spec they were among the first to figure out the
problem and write a program to bring RAM up to spec. Thank goodness that
long time programmer of the Eudora post office program for Macs finally
wrote a freeware utility that did the same thing on most RAM. I've wandered
off the main issue but you make an excellent argument why I shouldn't have
bought 133MHz Dimms in *anticipation* that they *might* migrate to the
next family or two of G4 Macs. Your comments present a very logical
argument for making certain that the RAM mhz correctly matches the bus.
- by Haenk April 8, 2005 5:47 AM PDT
- This seems to be a rather common problem, especialle with iBook G4s - with "factory new" machines. There are two possible solutions:
- Like this Reply to this comment
-
(5 Comments)- Apple doesn't test the sockets
- Apple sells refurbished, not thoroughly tested machines as "new"
Actually both seems to be common. We have a whole lot of customers with iBook G4s being shipped from Asia with preinstalled german OS. This seems to be very unusal, since they usually only have a bootloader installed.
A couple of customers had logic board replacements (mainly PowerBooks), with logic boards having one defective socket.
After all, Apples QA seems to be quite bad, considering the profit being made on these machines.