I'd like to know two things: - Max amount of RAM and - quickest RAM that goes into a MacbookPro current (2015 second half) version which I believe is called 2012 version.

I went to www.crucial.com where the suggested product for me was CT3373650. It is DDR3 PC3-12800 • CL=11 • Unbuffered • NON-ECC • DDR3-1600 • 1.35V • 1024Meg x 64. Right.

SIZE: Basically Apple says that 8GB is the most it supports. You can find many articles saying it supports 16GB no prob. Right. Does it support 32GB? Does it support CT2KIT204864BF160B? Which comes with similar specs if I'm right just it's 2048Meg x 64; which I believe is the same as CT2K8G3S160BM (just the first link is a marketing thing)

SPEED: I was searching for same spec just faster (lower CL) ones so I ended up with these: CT2K8G3S1339M and BLS2K8G3N169ES4 which both seem to have same specs just with lower CL. I asked Crucial in chat and they said they do Not recommend these, they will not work. As of my knowledge If you put a faster RAM into your computer all it will happen is that the CPU won't wait that much: a RAM is always slower than a CPU is (let's say always for this example).

So my question if Crucial is right or wrong: will I be able to use CL 9 RAM in this computer?

I haven't found a 2X16GB faster so no example for that one...

(Sorry for not putting up links. I don't have enough reputation to do it.)

  • Wait what? Apple supports waaaaay more than 8GB in their products. While it may not be able to access all the ram that it provides, it can definitely access more than that. Where did you find that out? (You should be able to put links into a comment, and then if you want, I can put them into the question for you :D )
    – Zizouz212
    Oct 31 '15 at 1:14
  • Hi, support.apple.com/en-us/HT201165#1 explains it besides many other tech docs. Oct 31 '15 at 1:51
  • So the recommendation by Crucial is: crucial.com/usa/en/ct2k8g3s160bm wheres a faster one would be: crucial.com/usa/en/bls2k8g3n169es4 which is CL 9. Will it work? Oct 31 '15 at 3:22

The CL (CAS, or Column Access Strobe Latency) will be upclocked if it is too low. This means that even if you bought ultra fast RAM, your Macbook will slow it down so it can use the RAM.


According to Apple's Macbook Pro 13 configuration page for your model (MD101LL), your Macbook Pro can officially take a maximum of 1600MHz RAM. Sure, you can put in even faster RAM, but it will be downclocked to 1600MHz.

I've found nothing that states it is able to use faster RAM. Still, 1600MHz is pretty fast and you generally won't notice the difference even if the Macbook was able to use faster RAM.

The laptop can only use CL11 RAM (there's literally no relevant results when searching Google for CL10 RAM for this Macbook model). This isn't surprising; this model isn't designed to be a workhorse; it can be compared to £300 Windows laptops- if you want something faster, you'll have to upgrade to a more expensive model.

Type & Capacity

Apple officially states that your machine can take a maximum of 8GB worth of DD3L modules, but however many vendors have found that the maximum RAM the machine can take is 16GB DDR3L.

No, it does not support 32GB.

Module Suggestions

There'll be absolutely no point in using RAM faster than 1600MHz or greater than 2x 8GB DDR3L modules.

The modules that Crucial suggested are the correct ones to use, and the fastest your model will be able to support. If the Crucial Memory Scanner is available for OSX (I'm unsure if it is), then any RAM modules that it suggests to you are guaranteed to be compatible.

  • Hi, thanks for your answer. I'd like to talk about things you mentioned: SPEED: I agree the RAM will get clock from machine, whatever it is. CAPACITY: can you reference anything your answer is based on? CL: your answer is against my university studies where we were tough that whenever the CPU needs data from memory it tells the memory and will wait for it, if the memory needs 1 cycle time or 1000 to give the data it will wait that many cycles, as a conclusion it's always the CPU that waits for the memory never the other way (in case of reading).Why would CPU tell the memory not to supply data? Nov 1 '15 at 10:00
  • @user3563097 See my edit. CL is latency; you want the lowest possible the machine is able to support.
    – AStopher
    Nov 1 '15 at 10:01
  • Why would the CPU tell the memory not to supply data what it's already waiting for? Nov 1 '15 at 10:10
  • 1
    @user3563097, because it can't trust the data to be accurate. It takes time for electrical signals to change from 0 to 1 or 1 to 0. If the data shows up faster than the memory controller is designed to handle, some of it will get scrambled.
    – Mark
    Nov 1 '15 at 10:34
  • @user3563097 That's off-topic for this website, but the CPU can only work with memory as fast as it is capable of using; any higher and it must slow the memory down.
    – AStopher
    Nov 1 '15 at 14:50

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