MacBook Pro does not recognise new RAM

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Level 1

4 points

MacBook Pro does not recognise new RAM

I attempted to upgrade the RAM of my MacBook Pro (15inch, late 2008, 2.4 GHz, OS 10.6.8) from 4 GB to 8 GB.

I removed the 2 X 2 GB RAM sticks and installed the 2 X 4 GB RAM sticks which I purchased from a reputable supplier (Crucial).

When I start up, I get the gray screen with the Apple logo and no further. However, when I launch the computer in Safe Boot mode, the system launches perfectly, and About this Mac/System Profiler have no problem seeing the two 4 GB memory sticks.

I did a test using the Rember app, and it showed that there was 8 GB installed.

I then installed each of the new RAM sticks on their own — both work perfectly.

Can anybody throw light on why they work OK on their own but not together?

If they work together in Safe Boot mode does this suggest a software issue?

Posted on Mar 23, 2015 5:47 AM

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Answer 1

OGELTHORPE

Level 9

57,305 points

Mar 23, 2015 5:50 AM in response to trmartin

The correct RAM specifications for your MBP are: 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM. Is that what was installed?

Ciao.

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Answer 2

trmartin Author

Level 1

4 points

Mar 23, 2015 8:37 AM in response to OGELTHORPE

The markings on the RAM sticks have the following text: 4 GB DDR3 - 1066 SODIMM MAC. There is nothing that says 204-pin PC3-8500.

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Answer 3

OGELTHORPE

Level 9

57,305 points

Mar 23, 2015 8:49 AM in response to trmartin

If the modules were other that 204 pins, you could not install them. 🙂

Did you try the new modules each on both bays?

If you reinstall the original modules, are they both accepted?

Open System Profiler>Memory. Are both modules recognized?

Ciao.

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Answer 4

trmartin Author

Level 1

4 points

Mar 23, 2015 10:04 AM in response to OGELTHORPE

Hello Ogelthorpe

I have only installed the indivdual RAM modules in one bay only; will try the second bay in the next day or so.

I had re-installed the previous RAM modules and they both work OK (and are recognized by System Profiler).

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Answer 5

trmartin Author

Level 1

4 points

Mar 26, 2015 1:28 PM in response to trmartin

I found that the 4GB RAM stick did not work in the second bay.

So I put it back in the first bay and put one of the old 2 GB RAM sticks in the second bay, and voilà, it worked — I have now 6 GB of RAM!

But one of my old questions still is unanswered: when I installed the 2 X 4 GB sticks, they both worked under Safe Boot mode — why would this be the case?

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Answer 6

OGELTHORPE

Level 9

57,305 points

Mar 26, 2015 1:39 PM in response to trmartin

trmartin wrote:

I found that the 4GB RAM stick did not work in the second bay.

Both 4 GB modules?

So I put it back in the first bay and put one of the old 2 GB RAM sticks in the second bay, and voilà, it worked — I have now 6 GB of RAM!

Your MBP should be able to accept 8 GB RAM.

But one of my old questions still is unanswered: when I installed the 2 X 4 GB sticks, they both worked under Safe Boot mode — why would this be the case?

I do not know. 😟

Ciao.

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