s.j.richardson
Level 1
(0 points)
Q: 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
petepete0pete
Level 1
(10 points)
i had (have) exactly the same problem, and the same computer (macbook pro 5,5). i'm convinced that its a design flaw with this logic board, and is something you just have to live with. what makes me think this?
1) i've only ever used 10.6 on this computer, so i know that the software upgrade is not the issue. it's happened on every sub-version of 10.6 with me. it 100% definitely for sure happens on SL. your noticing it on OS upgrade must have just been a coincidence.
2) i brought this computer to the apple store for apple-care-covered service when i first encountered it, which was in 2010. they were convinced it was ram, and so replaced the ram. problem persisted. they replaced the logic board. twice. problem persisted. i upgraded my ram with nice OWC ram, the problem still persists (BUT i will say that it happens less often now, not coincidentally related to the fact that the PCB on the new 4GB ram sticks were a fraction of a millimeter thicker than the old 2GB sticks). i know that the ram, and all the logic boards were really replaced because the ram had different serial numbers (reported in System Profiler), and the cpu id used for some copy protection changed with each new motherboard. further, i know it wasn't the ram, because even within only one set of individual logic boards/ram sticks, it was always the same slot that would go inactive, even if you swapped the sticks. again, this could be verified by serial number in system profiler to make sure they were actually switched.
3) when does the problem occur? often it will fail to wake from sleep. this is because half the ram disappeared, resulting in an incomplete loaded system, and thus failure. it fails to wake from hibernate in this situation as well, since the sleep image is twice the size of the hobbled ram. if you reboot verbose from this situation, you'll see the "sleep failure code 0x000015" (where i've surely gotten the number of 0's wrong, but you get the picture). for me, this seems to happen most often when either i carry the laptop around asleep and it gets a little jostled, or if i leave it asleep near a window, where the temperature can fluctuate quite a bit where i live. this point i see as directly related to the thickness of the ram sticks.
usually i can reslove the issue by shutting down again, and then rebooting, but there are times when the only fix is to open up the back and re-seat the ram sticks. needless to say, this is frustrating, and at first points to fautly (as in failing) hardware, but given what i've gone through with this, i think its just majorly inconvenient and not a sign of hardware failure.
except for this issue, my computer runs flawlessly. if you never rely on sleep, then it doesn't seem to be as much of a problem, at least for me, as i seem to always have full ram if i startup from a shut-down state. it seems unlikely to be a malfunction with this many different components. this points to design flaw.
i'm pretty sure the person on that other forum that was linked to wasn't lying, as the problem sounded all too familiar. that person reported that Bank1 was always the slot that went dead. that's also the slot that always went dead on mine. Bank0 always shows up.
(i think this issue might be underreported, as many users simply might not notice that their ram is missing.)
