Welcome to the MacNN Forums.

[Edit: A guide to MacBook Pro RAM upgrades has been added here.]

There appears to be some confusion about RAM upgrade possibilities on MacBooks. Here's an attempt to summarize what possibilities there are.

All MacBooks released to date have two RAM slots for SO-DIMMs (DDR2-SDRAM, PC2-5300, 667 MHz, 200 pins *). These are the maximum RAM upgrades for all MacBooks:
MacBook with Core Duo (May 2006 - Nov 2006): 2GB **
MacBook with Core 2 Duo "early" (Nov 2006 - Nov 2007): 3GB / 4GB ***
MacBook with Core 2 Duo "late" (Nov 2007 - current): 4GB

To find out which C2D MacBook you have you can check the FSB clock or the GPU: If you have a 667 MHz FSB and a GMA 950 (IOW you have an Intel 945GM "Calistoga" chipset) you have an early C2D MB. If you have a 800 MHz FSB and a GMA X3100 (IOW you have an Intel GM965 "Crestline" chipset) you have a late C2D MacBook.

A final word on matched DIMM pairs. It is true that memory bandwidth is increased by installing matched memory modules. In actually benchmarks this is something that is most noticed in GPU-dependent tasks (like 3D games) on systems with integrated graphics (like the MacBook). The reason for this is that the GPU has to use RAM as video memory (rather than using dedicated VRAM over a dedicated bus) which means memory bandwidth can become a limitation. Therefore, if you are interested in getting the maximum possible frame rate, you would probably want to install memory in matched pairs. However, this doesn't mean that less matched memory is better than more unmatched memory! If your system is paging out to disk because not enough memory is available (this is something you can find out by looking at Activity Monitor's "System Memory" tab) this will cause a huge performance decrease. This effect is orders of magnitude larger than the slight performance reduction due to unmatched memory pairs. Therefore: If you're paging out with 2 GB of matched memory, DO NOT hesitate to upgrade to an unmatched 3 GB! Of course going to 4 GB would be even better (if your MB supports it).


*) You can also use 800 MHz PC2-6400 DIMMs if you like. They will work. However they will in any case run at the memory bus clock speed of 667 MHz. There will be no performance advantage.

**) The Calistoga chipset supports addressing of up to 3GB, but Apple limited the CD MacBooks to 2GB in firmware.

***) Although you can install 2x2GB RAM in the early C2D MacBook for a total of 4GB, the chipset has an addressing limitation of 3GB. This is not something software, the OS or firmware could change - it is an inherent limitation of this Intel chipset. If you install 4GB in an early C2D MacBook the system will recognize the total amount of RAM, but you actually won't be able to use the last GB. Unless 2x2GB is cheaper (or more easily available) than an unmatched 3GB or you are concerned with maximizing GPU performance at all cost (and hence want matched pairs), there is no reason to install more than 3 GB in an early C2D MB.

Excellent FAQ. Thank you Simon.

Stickied.

In the interest of thoroughness, the first group should begin with "May '06".

You're absolutely right. My oversight. It's fixed now.

Compliments to Simon, great thread, very informative! I always see loads of people around the macbook forums asking how much RAM they can put in there computer or whatever, hopefully this will fix it!

I have the late 2007 Macbook which came with 2pcs x 500MB RAM. Lately, I've been given one stick of 2GB RAM taken from a similar Macbook.

Q1. Would it be inadvisable to replace one of factory-installed 512MB ram with this 2GB ram?

Q2. If okay, which slot should the 2GB be replacing; the slot closer to the power plug, or furthest?

Thanks.

No. If you experience page outs with 1GB (which I'm guessing you are) you definitely should upgrade to 2.5GB. Don't worry about the unmatched DIMMs. You can get a second 2GB DIMM if you want later.

Doesn't matter. Swap the DIMM you find easier to get to. Personally I'd go for the one at the center (that is the one further away from the power plug) just because there I have more space on both sides.

I am looking to upgrade my macbook and previously thought the limit was 2GB, but it appears it can handle 3GB. I have a C2D early edition as my GMA is 950 and FSB is 667 mhz (I bought it early Dec 06).

I was just on the Apple website to see what they suggested for RAM upgrades and it costs $300 for 2x1GB sticks!!! So, I began to look elsewhere and found this impressive forum.

My questions are:
1) Does my macbook really recognize 3GBs?
2) If yes, why doesn't apple promote this? It is a good thing isn't it?

Yes, just as it says in the very post of this thread.

Yes, it is. But in Apple's opinion an even better thing is if you had bought a C2D MBP that was advertised to support 3GB.

In the past Apple has often understated the max memory capacity. It used to be common that their max spec would be the number of slots times the max DIMM capacity at launch time. Later on when larger DIMMs came out people realized their max RAM was higher, yet Apple never changed the original specs.

And BTW, never buy extra RAM form Apple. You can get the same DIMMs with a longer warranty for less elsewhere. Some like OWC or Crucial, others prefer Newegg.

Hi,

I just purchased a macbook and i'm loving it. It is a refurb with an Intel Core 2 Duo 2.2 ghz processor with 1 gb of ram. I'm interested in upgrading my MB to at least 2 GB of ram. I did a bit of research and I discovered the 'System Profiler' which pretty much breaks down your system and states everything in it.

When I go to the 'Memory' section of this profiler, under the slots section, I see
BANK 1/DIMM0 1 GB DDR2 SDRAM 667 Mhz OK
BANK 0/DIMM0 Empty Empty Empty Empty

So does this mean that there is currently 1 stick of 1gb ram currently installed? I wanted to check things out online before I pry my new MB open and do something wrong :S.

Thanks!

Yes. You now have one free slot which will take a 1 GB or 2 GB SO-DIMM.

Thanks for the quick reply.

Does it matter which type of ram I decide to use? I went on to the Corsair Website
Welcome to Corsair :: Notebook Memory Product Information

and they have another section just for mac's. I would think that it shouldn't matter since they're both SODIMMs, with the same number of pins, and speed. Just double checking.

Thanks in advance!

It's right up there in the very first post: get DDR2-SDRAM, PC2-5300, 667 MHz, 200 pins. 800MHz PC2-6400 SO-DIMMs will work too.

thanks alot

Hello Simon

Thank you for the informative thread. I have an early C2D and purchased a 2x2GB RAM, however after installing it, my keyboard started to freeze and the caplock remained litted on. Now, my keyboard isn't working at all. Do you think it is due to installing a 4GB ram? Do you foresee any potential problems in installing a 4GB RAM although the maximum is 3?

Also, you mentioned 'MacBook with Core 2 Duo "early" (Nov 2006 - Nov 2007): 3GB / 4GB ***', I have checked my MB and mine belongs to the Mid-2007 model according to the Apple website - and it states that the maximum RAM is 2GB. So is it okay to go beyond the stated 2GB? Thank you so much for taking time to answer my questions

Maybe the installation, maybe the RAM. Have you tried removing the new DIMMs and putting back the old ones?

No. Apart from not being able to use that last GB absolutely no problems are to be expected.

Yes. Apple's terminology is "Late 2006" and "Mid-2007" for what I referred to as "early C2D" models. Apple has a record of giving lower max RAM specs than what can actually be used in a Mac. Nothing to worry about. Again: no damage is caused by installing more RAM in a MB than what Apple originally specified. 4 GB should install perfectly fine in your MB and you will be able to use 3GB. If it doesn't work then either the installation went wrong, the RAM is bad, or there's a problem with your your MB's MLB.

does this apply for macbook pro's also?

In a certain sense yes, because the MBP and MB share chipsets.

All MacBook Pros released to date have two RAM slots for SO-DIMMs (DDR2-SDRAM, PC2-5300, 667 MHz, 200 pins *). These are the maximum RAM upgrades for all MacBook Pros:
CD MBPs (Jan 2006 - Sep 2006): 2GB **
C2D MBPs with 667 MHz FSB (Oct 2006 - May 2007): 3GB / 4GB ***
C2D MBPs with 800 MHz FSB (June 2007 - now): 4GB
[Do not confuse FSB speed with memory speed! 800 MHz FSB MBPs come with 667 MHz RAM. Check your FSB speed in Sys Profiler.]

*) You can also use 800 MHz PC2-6400 DIMMs if you like. They will work. However they will in any case run at the memory bus clock speed of 667 MHz. There will be no performance advantage.

**) The Calistoga chipset supports addressing of up to 3GB, but Apple limited the CD MacBook Pros to 2GB in firmware.

***) Although you can install 2x2GB RAM in the early C2D MacBook Pro for a total of 4GB, the chipset has an addressing limitation of 3GB. This is not something software, the OS or firmware could change - it is an inherent limitation of this Intel chipset. If you install 4GB in an early C2D MacBook Pro the system will recognize the total amount of RAM, but you actually won't be able to use the last GB. Unless 2x2GB is cheaper (or more easily available) than an unmatched 3GB, there is no reason to install more than 3 GB in an early C2D MBP.

My MacbookPro currently has two banks filled of DDR2 SDRAM @ 667 MHZ but was purchased in Dec 2007 (2.2 ghz/800mhz bus) Does this mean it is an "Early c2d mbp"? Do I upgrade to 3gb or will 4gb work. Sometimes the more i read the more i get confused. thx.

You are mixing up FSB and memory speed. This is a common problem. I added a comment in my previous post to clarify.

You have 667 MHz RAM, but that is the memory speed. Your FSB is still 800 MHz. That is quite common as modern Intel mobile chipsets always have higher FSB speeds than the actual memory interface bus speed. Having faster RAM than the memory interface bus speed is of no use. So since your 800 MHz FSB MBP has a 667 MHz memory interface bus it is sufficient to use 667 MHz RAM. The next Intel mobile chipset "Cantiga" will offer an FSB clock of 1067 MHz. The memory interface bus will still be 667 or 800 MHz though. Again in any case, FSB clock > required RAM speed.

In short: You have a 800 MHz FSB MBP that will accept (and make use of!) a total of 4 GB of RAM. Install two 2GB SO-DIMMs for maximum memory and performance.