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13" aluminum unibody, 2.0 or 2.4 GHz Core 2 Duo processor.

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I have a bad memory slot

I'm working on a MacBook Pro 13" 2.4GHz (Mid-2010) that has a beep every 5 seconds. After a bit of troubleshooting I found that the top memory slot is bad. The MacBook works fine with each 2GB memory module (installed one at a time) in the bottom slot. Anything installed in the top slot causes the beeping error. I have tried cleaning the pins of the slot with Isopropyl Alcohol and compressed air. Instead of replacing the Mother Board, I thought why not just run it with memory only in the bottom memory slot and instead of only 2GB, put in a 4GB module. It won't boot with the 4GB module installed. It hangs on the spinning sprocket. Normally, nobody would run a MacBook on a 0+4 configuration, but has anybody tried? I either have a bad memory stick or it's not possible. It runs fine in a 0+2 configuration.

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Are you sure you have the correct SIMMs for this system? are the SIMM's you have the same brand, spec and I/O speed (2GB SIMMs). If not your SIMM's may indeed be the issue not the socket.

Mixing different sized SIMM's can be tricky as the smaller sized SIMM needs to be in a given slot. But before you go into adding this 4GB SIMM make sure its I/O speed and specs are correct for this system.

Review your models memory requirements from Apples Tech Note:

The first slot (slot 0) needs to hold the smaller SIMM if you mix sizes. Running different sizes forces the computer into a slower I/O method. If you use the same size (matched set) your system will use inter-leaved I/O which is much faster!

I would try a fresh set of matched SIMMs (2 or 4GB) to make sure your going down the right path here.

In any case using the wrong type and speed of SIMM or you have a mis-matched set can create sporadic operation and cause the reaction you are seeing.

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Hi Dan:

Thanks for your response. Yes, it is Mac memory and the correct speed (PC3-8500 DDR3-1066). The problem I have with this Mother Board is it has a bad memory slot, so an unmatched set (if you can call it that, since the other slot is empty) is my only option for a cheap fix. It does run okay with only one 2GB module installed. I will try another memory module late tonight and let you guys know what I find.


Mix sizes - two different sized SIMMs, as an example one 2GB & one 4GB SIMM.

As I stated try using two SIMMs bought at the same time that meet spec (a matched set) to see if your slot is truly bad (I have two sets just for testing 2-4GB & 8GB) is the best way to check things out.

I have seen slots damaged by SIMM's that were to big (PCB thickness) cheap knock-offs. If you have a good dial caliper you could measure the thickness of the SIMMs PCB of the one that works Vs the ones that don't. Otherwise it's more likely a bad SIMM than a bad slot (if you don't see any visible damage).

If you want to go deep into this checkout this JEDEC doc:

Review Annex A - Raw Card A Module Configuration note the 7th column values, the number of address bits differ between the different sized SIMMs. Only the 8GB SIMM has a different column bit value.

One last point: Slot 0 needs to be populated first to work correctly. If Slot 0 is broken you maybe able to get a smaller sized SIMM to work in Slot 1 but larger sized SIMM's won't play well in Slot 1 by them selves.


It turned out that the first 4GB module was bad. I tried another and it works perfectly. The configuration: slot 0=empty, slot 1=4GB is possible. Mayer: I didn't have a smaller sized module to try your suggestion. Thanks guys.


Was slot 0 able to work at all?


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Sometimes a bad slot will take a lessor GB memory module and run fine, if you have a 1 GB or a 512K give it a try in the bad slot.

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