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I have a rather old motherboard with 4 DDR2 slots, all occupied.

I bought the board, RAM modules, and CPU from an acquaintance, second hand, so I do not know the exact history of the problem.

The problem is:

On rare occasions, the machine fails to boot. i.e. When I press the power button:

  1. I see no display at all
  2. The CPU fan runs, stops, runs.. repeatedly with the same frequency.
  3. The Speaker does not make the usual on-boot 'beep'

When I asked the original owner about this problem, he asked me to 'pull out the RAM modules and switch their slots'.

I was sceptical about this solution, but I tried it, and the machine booted.

Since then, whenever this occurs, I have found a cause-effect relationship between 'switching the modules' and 'the machine succeeding in booting'.

My question is: Why does switching the modules (temporarily) fix the failure to boot? It does not seem logical. I guess the answer would also need to explain why this can happen in the first place.


If it matters: The modules sit flush in the slots (they are pushed in properly). They are Corsair XMS2 modules of 1GB each, the heatsinks are thick enough that they (almost) touch each other when on the board.

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Have you ever tested the Ram? Like... with memtest86.com –  Bon Gart May 9 '12 at 15:50
    
@BonGart - +1. This is good advice. No I haven't. I will try it, at some point. Although, I don't see that will help me understand why switching modules works. –  ArjunShankar May 9 '12 at 15:56
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Because one of the modules might not be working, regardless of what slot you put it in. I remember a windows box I had with one (of 4) bad sticks. I was able to install Windows without error with that stick in the system, but I only saw issues when I transferred large files (got CRC errors). As far as corrosion is concerned, you can use a pencil eraser to clean the contacts on the Ram itself. If the Ram goes into the slots easily, it might be that they are too lose. It might even be that you only need to wiggle them. But checking to see if any are bad is still a step. –  Bon Gart May 9 '12 at 16:04
    
@BonGart - Yes, you could be right about the bad module. I will definitely test the modules. –  ArjunShankar May 9 '12 at 16:09
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1 Answer

up vote 1 down vote accepted

Since the mainboard and RAM are old, there might be the possibility that the connector is dirty (oxidized).

Why removing and re-inserting the modules 'fixes' it

The friction generated when re-inserting the modules probably scrapes off the oxidized material, thus providing better electrical connectivity.

How to verify this

Next time the problem occurs, try removing and re-inserting the modules in the same slot. This should work as well.

Or even better, clean the contacts on RAM with contact cleaner.

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+1. This sounds logical. I will try reinserting into the same module the next time the problem occurs. The problem is rare, so I'm not sure when I'll be able to 'confirm' whether what you say is right. However, what you say sounds quite convincing. –  ArjunShankar May 9 '12 at 15:58
    
please, go ahead an try :-) –  chmod May 9 '12 at 16:00
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