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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Desktops > Interesting Memory Problem With MDD PowerMac

Interesting Memory Problem With MDD PowerMac
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Agent69
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Feb 3, 2004, 10:09 PM
 
As you all probably know, the mirrored drive door PowerMac G4 supports 2GB of RAM. Since RAM is cheap, I ordered 2GB of RAM from Crucial (4 512MB sticks of PC2700 RAM). If any three of the sticks are installed, the computer will run fine. But if I install all four of them at once, the computer will occassionally lock up. (And yes, Mac OS X and System Profiler both see and report 2GB).

I tried the Apple Hardware Diagnostic disk. It has no problem with any particular piece or combonation of RAM. But if I try it with all four sticks installed, then it eventually panics and freezes during the memory check.

Now, I know that I could just run with 1.5GB of RAM, which is more than enough for my needs, but I am concerned that this could be an indication of a problem with the motherboard. Any suggestions before I call Apple?
Agent69
     
Simon
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Feb 4, 2004, 11:38 AM
 
When you had only three sticks installed, did you switch the slots or did you always leave the same slot empty?
     
Agent69  (op)
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Feb 4, 2004, 03:55 PM
 
Same slot was always empty. Does is matter which slots I use?
Agent69
     
Mac Write
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Feb 4, 2004, 07:32 PM
 
Originally posted by Agent69:
Same slot was always empty. Does is matter which slots I use?
Yes it does matter. try putting one of the working DIMMs in in the other slot and see if it still works. either the RAM is bad, or the slot is dead.
Get busy living or get busy dying
--Stephen King
     
Simon
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Feb 5, 2004, 04:08 AM
 
Originally posted by Mac Write:
Yes it does matter. try putting one of the working DIMMs in in the other slot and see if it still works. either the RAM is bad, or the slot is dead.
Exactly, because you claimed the hardware check didn't find bad RAM, so I thought it could be a bad slot. Therefore you should try to see if changing the empty slot changes the behavior.

Of course, if it's a bad slot it's amazing the hardware check didn't report a bad DIMM nevertheless.

Finding a bad slot won't get you that far however. You'll have to take the Mac in and get a new board, but it would be interesting to know...
     
Agent69  (op)
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Apr 1, 2004, 01:45 PM
 
After a lot of checking, it was determined that there was a problem with the J20 RAM slot on the motherboard. When I could afford it, I purchased Applecare and Apple had a guy come out to the house and replace the motherboard. It works great now and all 2 gigabytes of RAM is usable. From the looks of the box the replacement motherboard was in, I would say it was a new motherboard and not a refurb.

Perhaps the one funny thing is that now I have no serial number listed in System Profiler or in the "About This Mac" dialog box. Apple says this is normal in a motherboard replacement situation and that Mac's serial number remains unchanged. (I point this out in case it happens to someone else.)
Agent69
     
   
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