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On Tue, 27 Jan 2015 15:28:11 -0800 walt wrote: |
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> Yesterday I installed 4GB more of RAM in this machine for a total of 8GB, and |
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> the machine soon began random segfaulting and even a kernel crash or two, so |
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> obviously I suspected the new RAM was faulty. |
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> |
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> I let memtest86+ run overnight and it found zero memory errors. Today I |
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> exchanged the new RAM anyway and got a different brand this time, and |
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> that fixed the problem. |
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> |
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> My question is why didn't memtest86+ find any errors? Could it be that the |
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> first RAM I bought was actually okay but this machine didn't like it for some |
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> reason? Both were DDR3/1333MHz, just from different manufacturers. |
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As an addition to earlier posted comments: |
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1) memtest86+ has a bit fade test which is not enabled by default |
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(at least for 4.x branch which is the latest in tree now), so |
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you have to enable and run it manually. IIRC it is enabled by |
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default in 5.x branch (bug pending in bugzilla). By the way 5.x |
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have some additional tests which may find faults unknown to 4.x |
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2) The same frequency is not enough to guarantee memory banks |
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compatibility. They may require different timings or, less probably, |
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voltage. Some BIOS tuning may help here. |
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3) Memory may be (un)buffered, (un)registered, ecc/non-ecc. Many of |
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these combinations are not compatible with each other. |
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4) In some rare cases even banks with the same parameters from |
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different manufacturers are not compatible due to technological |
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differences (this goes down to how logical circuits are |
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implemented). |
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Best regards, |
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Andrew Savchenko |
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