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

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.)

I have a macbook pro that i bought in 2009 and for the last month or so Its been having a multitude of issues. First off It won't detect my second stick of RAM. It says i only have 2 GB now, instead of 4 but thats just been the last few days. My biggest problem is that whenever i close the lid to my macbook it won't turn back on and it will randomly turn its self off and the only way to turn it back on is to hold the power button for 30 seconds then press it again. I was running snow leopard when the narcolepsy started happening and it ****** me off so ******* much, then mountain lion came out and i bought and installed that. Didn't fix the problem at all and over the last few days my macbook stopped displaying all 4 gb of ram. I brought it into my local mac repair shop (macrotronics based out of Lebanon and complete with greedy Lebanese employees who lie through their teeth) where they replaced the ram, still nothing. They replaced the screen thinking that the screen was causing the issue with the narcolepsy but it didn't fix the issue either. They refused to change the motherboard they simple "cleaned" it. I tried to see if it was a software issue so tonight i clean installed snow leopard and it still has the narcolepsy and it still doesn't display all 4GB of RAM. When i got the macbook back it did show the 4GB of RAM but after he shut it down and gave it back to me it stopped showing all 4GB so i'm seriously ****** off. The issue is not specific to Mountain Lion at all. Its a hardware issue. I'm going to contact apple directly since macrotonics refuses to replace my motherboard and cpu, they are an "authorized apple service provider" but they are unwilling to spend more than one hour trying to repair my computer and they won't replace my mac they even said it was completely impossible to get it 100% refurbished.

I'm experiencing the exact same thing. My 2009 macbook pro (still running snow leopard) has recently started to shut down periodically, and can only be woken by long presses of the power button.

I also went to upgrade from 4gb ram to 8gb and noticed it was only recognizing one stick. Tried swapping the sticks in the different sockets and it always refused to recognize the same socket.

Can't see anything affecting the socket connection. Any chance I could convince apple to fix this without paying for a new logic board?

HI!

I'd like to report the same thing! Back in February, 2012, my mid 2009 macbook pro 15" has crashed..

In my case, it actually killed the hard drive and the RAM in slot1.

The hard drive is replaced and I was one RAM, because of money issues, but last night my newly bought RAMs have arrived. 2x4GB corsair RAMs and when I installed them, everything was just fine. I've checked it, it was really 8GB what the mac recognised.

I put the mac to sleep and the next time I opened it, the same thing happend like back then. The mac wouldnt wake (this is how I realised that one RAM was missing in the first place, back in April, 2012..)

Im quite sure that this time at least none of the RAMs got damaged, however, I was unable to solve the issue with simply switching them..

I found thins article and after trying all the things that I've read here, finally it was 8GB again....!

I've tried switching them with a PRAM reset right after ir, I've tried SMC reset, I've tried holding down power button while led started blinking really fast on turning on...... I've all these in many differend combination and order..

I've even tried to take one RAM out and leave just one in slot0. Then take out the RAM and put the other one into its place (slot0 again)... I thought, maybe on startup, the mac is able to somehow initialise the RAM in slot0, while it is unable to do so in slot1........ I've even tried this with all the things mentioned above (differend orders and different combinations).....

My conclusion is that there is no 100% working way to solve this, so the problem is not really logical. It's a bit like a lottery....

When suddenly the mac was able to see all 8GB again, sleep ruined it again (did that on purpose), and Ive tried to redo all the things prior to regaining all the RAMs and it was not working again...

One time, the mac was unable to recognise slot1 (and RAM in it), however, it was saying that not 8, but 7.75GB was installed..... (Ive got to attach the printscreen of this....!)

So.. Maybe I'm not too helpful, but If someone solved this already, please let me know!

One more thing, if I only use slot0, and I put nothing to slot1, THERE IS NO PROBLEM.. AT ALL.. 100% sure about thism since I was using my mac from April to now with only one RAM installed.

Here's the prinscreen and all the best from Hungary!

I believe I have found a DEFINITIVE solution to an identifiable problem. I have a Macbook Pro 13" 2010, with 8 gb ram. In the last 6 months, I have had Bank 1 (4 gb) disappearing on me intermittently. In the last two months, I had consistent loss of 4 gb of ram, especially after restart. When I start cold (after 24 hours), it recognizes 8 gb, but if I restart, it recognizes only 4 gb. I would stick the macbook in the freezer for 10 min. Of course, I get 8 gb.

So what the ****?

I have gone through every thread google has to offer. No solution, except that the best explanation was that circuit board was getting old. It explains why Apple created new vents for the new Macbooks. I also believe they soldered in the ram for this exact reason.

So I got sick of it and opened up the macbook, unscrewed, removed, cleaned out the fan, unscrewed the circuit board removed the Ram. I even unscrewed the 4 screws around the plastic RAM holder. I cleaned everything out with 91% isopropyl alcohol and everything inside the RAM holder and the ram itself.

I tested each RAM in each slot alone and carefully turned the computer on. 4 gb as expected. Both banks worked. Both RAM functioned fine alone in each of the banks.

So what the ****?

I popped both back in.....8 gb. Restarted it. 8 gb. I did this 10 x. Every time 8gb.

So I thought it was because I did a great "cleaning" job. I screwed everything back in, circuit board, RAM "holder", etc. Restarted....7.75 gb. !?

Restarted again.... 4gb?! DId this 10x, 4 gb.

What the ****?

I opened everything and LOOSENED the four screws around the Ram HOLDER.....

8 gb ever since!

I believe with time, the awesome heat from the macbook pro eventually warps the circuit board. My macbook was just under 3 years old and started to have this problem. The four screws holding the ram holder in start to tighten up with heat and somehow it does not recognize one bank. That's why when I freeze the macbook, it gets the other bank back. By loosening the screws, it allows the circuitboard expansion with heat.

Anyways, I hope that helps.

I tried quadturbo's method and it didn't work work ... My current guess is, the RAM slot degraded as Quadturbo's analysis, and cannot align the RAM to a correct contact positions. To be specific, take a look at my illustration:

Notice that the two clips on the left and right are used to hold the rams in a horizontal position, otherwise they will bend upwards. I took a close look at those clips and found that the plastic wore out and cannot hold them as original. I don't have great ways to fix them, so I just cropped some papers and insert them between the RAMs and the back edges on the body, hoping they can help tucking the RAMs.

As far as I can see, this fix the issue. Not sure if it is the real cause, just my two cents.

Thanks for the quick respone. I have been trolling the internet for days with this problem. I have found a few similare threads that detail this and in one of them someone is claiming apple replaced the logic board and the ram and the problem persisted.

https://discussions.apple.com/thread/2378828?answerId=11276081022#11276081022

It seems to be a reoccuring problem with this generation of 2009-10 macbooks.

So it continues to do even after you have physically made sure the ram placement is ok? I am having the same exact problem as you. I have a mid 2010 MBP with 4gb with only 2 showing up after sleep, restart unless I do the ram reset while booting.

Hi.

Yes, I have an idea.

It maybe that the RAM you currently have installed is somehow faulty. It may have been faulty from day one, and perhaps there are certain things in the now OS that make it less tolerant of any RAM faults that might exist.

If you still have the original RAM that came with the machine, I suggest removing the upgrade and reinstalling the oem modules. See if that helps. If the symptoms disappear, it is an indication that the upgrade(s) is/are the problem. If you bought from a reputable retailer, many manufacturers stand behind their product with lifetime warranties.

Bueller 😉

I suspect the one RAM slot is going bad. It is making intermittent contact with the Logic board. This can happen from age and heat/cool cycling over time and poor parts assembly. Contrary to what most people think Apple computers are not built any better then any other brand. They do not use any better parts and are not assembled any better then any other.

The only way to full fix this issue is to more then likely replace the Logic board which in the end you'd be better off just buying a New Computer.

This is a good point, and after carefully rereading your original post, I believe Shootist007's evaluation may be more likely. Especially inlight of the fact that after swapping the RAM modules, the same memory slot is failing to register with the OS.

😟

Just a coincidence and or the heat generated in the RAM and the slot with the install of the New OS just made it show up now. With the install of a new OS there is a lot of reading and writing to and from the RAM to the HDD. More then in any normal operations.

If you made a Time Machine backup from just before you did the upgrade to Mt Lion you could always make a second partition on your drive, or use an external, and restore that TM backup so you can boot to Lion and check to see it the RAM shows up all the time.

EDIT:

Yes do a clean install of SL and check.

This didn't happen to me until I upgraded back to Lion the second time. I went from Lion back to a clean install of Snow Leopard back to Lion and then I had the problem with it not waking from sleep. The first instance with Lion I had no problems. So I decided to go back and do another install of Snow Leopard and the problem stayed with me. I am now on 10.8.1 and the problem remains the same.

I have, kind of, solved the sleep problems by putting hibernatemode at 25. This has allowed me to wake the computer up without a hard reset, but when I do wake it up it makes that hard drive spinning noise twice, almost as if it is waking up twice. Then, back to 2gb unless I reset the ram. I am going to take the case off tomorrow and just make sure everything is ok in there, but other than that I am just hoping it's not the logic board as my computer is a few years old now. I may also just throw a 4gb into the one thats working.

Memtest has found no problems either, both with 2gb and 4gb showing.

Thanks for the help everyone, this is really driving me nuts and answers are hard to come by.