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Can you have uneven memory in the two memory slots?

Hey, I was looking to upgrade my mac book pros memory when I saw i have 2 gb memory in each slot, and I was wondering can you have 4 gb of memory in one slot and 2 gb in the other or do both slots need to be even. Thanks in advance.

EDIT: I read the answers and Im a but confuse, So I will my computer run faster then before with the 4 and 2 gb? Or will it be the same because of the uneven-ness.

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Deck the Halls
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To clarify things here:

Yes, you can have different sized SIMMs in the slots as long as each meets the needed speed for the given model. You may also be required into installing the smaller SIMM in a given slot. While you will have more memory to use the addressing will be slower.

If at all possible use the same sized SIMMs by the same manufacture (as some manufactures chips may not play together well) so you can use inter-leaved mode.

When you have the same sized SIMM in each slot the faster inter-leaved mode is used.

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Well I have a late 2011 MacBook Pro 15 and I bought it at that time, 2011. Well, I did the 2gb in one slot which is still the apple standard and just replace the second slot with "ramjet" brand 8gb making it 10gb. Well, I've had that upgraded since last October 2013 and on may 20th 2014 after 8 months my MacBook Pro malfunctioned. I had to do the flat rate fix of $310 thru apple genious to have the logic board and both slot rams replaced back to 4gb ram. I lost 3.5 days. They gave me back in a static free envelope the aftermarket ramjet 8gb. They mentioned long term use of unmatched ram can put tremendous strain on the bigger ram causing constant over heating build up on part of the logic board it will start failing. I do a lot of heavy processing software like Photoshop CS5 and Final Cut Pro x and running lots of apps together. The apple agent said it's was like having unequal tire size. So they recommend equal match ram sets. I'm going try to get some compensation from ramjet. They said it was "absolutely" fine with miss match. Nope. I've had others tell me now should be matched.

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Can you take a good hires photo of the RamJet memory modules label and if you can the discreet chips labels post them here for us to check out. While we only use matched modules our selves. I can tell you using different sized modules are possible and shouldn't have caused your problem. I suspect the specs of the chips on the module are not correct here. You see, some chips pull more power (over heat) which is what I believe the Apple Genius noted was the cause of the system failing. The excessive heat damaged the memory slot (logic board). This would still have happened with a match set of these improper modules, if the specs are not correct.

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CAN you have uneven RAM chips? Absolutely! Will it run? It should for a while at least. The problem is that your system will become unstable and likely crash regularly. The best option is to get matched RAM.

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Why would it crash or become unstable?

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The system can become unstable only when you have the same size memory by different vendors as inter-leaved mode is more demanding. Yes, some SIMM's play nice, others not. If you want to get deep here it's the RAS & CAS speed (read & write) of the discrete memory segments between the SIMM's. Thats putting aside the SIMM's are correctly rated (I/O) for the given system. If not even mixed sized SIMM's could be unstable.

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Hi Dan. Not sure how to post a hi res photo here. I can tell you it's an 8GB chip. I spoke to Ramjet company. They said apple would try to blame aftermarket parts that may damage the standard apple products if found. Because my ram upgrade is an aftermarket they will try to blame it on uneven chip set. 2gb from standard apple ram and one 8gb from ramjet aftermarket. There is a sticker with numbers GPM1333NS3C98GBT. I can just make out on the sticker below that code PRINCETON. On each of the chips I see the following:

NANYA 1325

NT5CB512M8GN-DI

15579001GP 8 TW

I'm noticing that some dark chips are upside down on both sides. Alternating and there are 8 on each side. They are sending me another one and returning this defective one as I get a life time warranty. They also said that I may have a one of the odd defective logic boards because apple's pumping out thousands of these. Odd chances I may have one that would be short lived after 3 years. Most macs can live up to 10 or more years without any problem. He's right, I have a lesser macbook pro that's still working. Slower processing speed. But still outlasted this one on one run.

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When you post an answer or edit your answer posting you will have an editing ribbon just above the text field the far right blue square icon allows you to post the image (first uploading it).

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The layout of the chips are not always laid out in the same direction as you have noted. Without a good image I can't identify what you have to look the chips up.

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Here's what I found on NANYA Nanya Technology Corporation and here is their Part Numbering Guide for their modules. I would need the images to go deeper.

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what you're talking about off course you can my laptop is 4Gb and 8Gb Ram I'm using it since 6months ago with windows 10 and no problem I have noticed at all from using different size memory

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Hi Ethan,

I hope this no longer an issue for you however, as I understand it having unequal Ram size is not a huge problem, but you must make sure the Manufacturers are compatible, and operate at the same speed, or you will end up with instabilities with the system.

Such as, "Crashes, Freezes, and eventually over longer periods may even do damage to the MotherBoard, where over-heating can possibly occur. The reason this can happen is because one slot is working overtime and there is often a tendency for the machine to run much slower than it is actually capable of doing...

This is just my understanding having used Macs since 2002, and having replaced most of the Ram, Hard drives and Batteries myself.

I am by no means an expert in the matter, however I have had to learn the hard way on more than 1 occasion, which I can assure you tends to make you think twice about doing things without a little research into the possible outcomes 1st, that said, "if it aint broke, don't bother to fix it... Hope this has helped in some small way, Best of Luck Pal.

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Ethan will be eternally grateful.
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