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MacBook Pro loses access to 1 memory slot upon shutdown or reboot in OS X 10.8.1

I have had 4GB of RAM in my mid-2009 13-inch MacBook Pro since a few weeks after purchasing it in 2009. Until a couple of weeks ago, this machine has been running OS X 10.6.8 with no RAM issues. I wanted to wait for 10.8.1 before doing a clean install of Mountain Lion on this MacBook So, the day that 10.8.1 was released to the App Store I immediately purchased and downloaded the new OS. I then performed a clean install of the OS, got all my software setup, and all was right with my MacBook.

However, over the next week I noticed upon startup or reboot of the machine everything felt sluggish. I opened the activity monitor and clicked on the system memory tab, it showed 2GB. I immediately clicked on the About This Mac button to see how much RAM was installed, it showed only one 2GB stick installed (the other memory slot was empty). The next option I chose was to restart the computer. Upon startup it still only showed one 2GB stick. Next, I shutdown the computer, opened the back cover, and proceeded to remove both 2GB sticks of memory. I blew out the slots with compressed air, swapped the positions of each stick and reseated the memory.

I started up the computer and to my pleasant surprise both memory slots were recognizing 2GB each (4GB total). I thought this had permanently resolved the issue, but unfortunately after every shutdown or reboot my MacBook (without fail) loses access to the second memory slot, unless I remove and reseat the memory.

This problem did not start until after installing 10.8.1. I have tried countless SMC and PRAM resets. Please help.

MacBook Pro, OS X Mountain Lion (10.8.1), 13-inch, Mid 2009, 4GB RAM, 500GB

Posted on Sep 3, 2012 10:12 AM

55 replies

Nov 20, 2014 1:38 PM in response to quadturbo

As crazy as it sounds, I tried this, because I upgraded my RAM to 2 x 4GB sitcks from the original 2 x 1GB and I was getting errors in the bottom slot ( not sure if that is slot 0 or 1) ad described by others, except it would not even recognise the RAM and I was getting beeps on startup and no booting, then hanging and failing to restart from sleep mode,

This fix seemed to work. Running a hardware diagnostic overnight to check RAM sticks as well. Hopefully this will work because if not I will be stuck with 4GB in one slot only 😟

Nov 21, 2014 9:44 AM in response to s.j.richardson

So, given that the 1GB stick seems to work fine in Slot 0, and 4GB stick in slot 1, how much of a performance hit would I expect to get if I decided to run with it configured that way? Or should I just run 4GB in slot 1?

Nov 21, 2014 9:47 AM in response to bearMedicine

PS This didn't work permanently, but better than before. As per Fixerator's post, I guess I will just keep trying fiddling with the RAM socket screws 😕

tjh421

Level 1

5 points

Nov 21, 2014 11:26 AM in response to bearMedicine

I ended up replacing my logic board and everything works now.

Nov 22, 2014 4:52 AM in response to tjh421

How much did that cost? It might be worth a shot...

tjh421

Level 1

5 points

Nov 22, 2014 3:58 PM in response to bearMedicine

I paid $294 on Amazon and he's supposed to be giving me a $40 credit for mailing him my old logic board;

http://www.amazon.com/gp/product/B003CO1NHA/ref=oh_aui_detailpage_o03_s00?ie=UTF 8&psc=1

I found a youtube video with step by step instructions on how to replace it.

RkS909

Level 1

0 points

Jun 18, 2015 7:22 AM in response to quadturbo

Thanks for investigating and posting here. It was helpful for me and my MBP mid 2010 also. Same issue and symptoms. I have loosened the screws of the memory brackets and kept the computer backside lid open. Not seen the problem. Hope this is resolved.

Nov 12, 2015 12:53 PM in response to quadturbo

I have been fighting this problem for months. I tried loosening the four screws, and so far it has worked!

Jul 22, 2016 5:02 PM in response to s.j.richardson

We had the same issue, the system not recognizing the RAM.

If you are at this point, you have already gone thru how to remove RAM.

I'll just go in

We have 2 computers that we " did surgery" on. A 2009 macbook pro and a 2011 macbook pro.

When both computers said one of the slots were not recognized, we delved in a bit further.

What we did :

1. Do a proper shut down of the machine( from the apple drop down)

2. Unscrew back.

3. Remove the new ( not working) RAM..

4. Blow out the slots for any dust bunnies.

5.Re-insert RAM.

6. Unscrew ( just1 turn) all 4 screws around memory slot.

7. Screw back - back on.

8. Hold down Option-Command key with power button.

9. Release once screen turns gray

10. Check memory- and voila!

Thanks to the two different people who posted in the forum the different actions listed above.

Not sure which one made the system recognize the RAM, but it did.

Nov 28, 2017 1:05 AM in response to quadturbo

this worked for me and seems to have fixed my waking problems. Thank you!

MacBook Pro loses access to 1 memory slot upon shutdown or reboot in OS X 10.8.1