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How to install 6GB or 8GB memory in MacBook Pro

This page is dated. The 2011 MacBook Pro now accepts up to 16GB memory.

In November 2008, OWC introduced an exciting new option for 2007 and 2008 MacBook Pro users: a 4GB memory module that allows a total of 6GB of memory, an unprecedented breakthrough.

This is a big deal, as 6GB is in actuality more than 2GB more than 4GB! The usable memory on a 4GB system is around 3.2GB after booting, vs 5.2GB on a 6GB system. So having a 6GB module is more akin to having 62% more available memory.

When running multiple program together, such as Photoshop, Aperture, a RAW-file converter, Mail, Safari, etc, the extra 2GB can make a very large difference in performance, well beyond the apparently modest increase in memory. See the Photoshop test results for more.

Up to 8GB in the newest models

The bulk of the review that follows was written for the 6GB kit, but applies equally to the 8GB kit for the MacBook Pro 17" (see review).

The 2009 17" MacBook Pro accepts 8GB memory (two 4GB modules). This kit has now been used extensively in the review of the 17" model—it’s rock solid and highly recommended! Get the 8GB kit at OWC.

Update, April 2009: the newest 15" 2.66GHz and 2.93GHz also support 8GB. The 2.4GHz model supports a maximum of 6GB.

You can install 6GB or 8GB in the 17" MacBook Pro as 2GB + 4GB or 4GB + 4GB. Price-conscious users might want to try 6GB first to see if it meets their needs without going to 8GB.

Rock solid under severe load

Using the OWC 8GB kit (two 4GB modules), I ran the MemoryTester stress test for 5.6 hours at an ambient temperature of approximately 70°F (21°C). That’s 100% CPU usage of both cores, fast graphics enabled, continuous hard-drive access and the screen on full brightness. The MBP17 was rock solid, and only got moderately warm on the bottom or top. Amazing performance and a big improvement over the previous models, which could become uncomfortably hot. It also speaks well to the rock solid reliability of the OWC memory kit. Unfortunately the runtime was only a bit more than two hours, see the results.

Installation of the 6GB kit

OWC shipped me a 4GB and 2GB module for evaluation, but at first I installed just the 4GB module—my MacBook Pro 2.4GHz (2007 model) had two 2GB modules already installed. I popped the battery, removed 3 screws, and in seconds had swapped the top 2GB module for the OWC module. I screwed the screws, popped in the battery and was done: 2 minutes max.

A few days later, I replaced my remaining 2GB module with the 2GB OWC-supplied module—same reliable results. Regrettably, dual 4GB modules apparently cannot be made to work reliably, but perhaps OWC will work out a solution in the future.

Installation takes a bit longer in the new unibody (late 2008) MacBook Pro because accessing the memory slots requires removing and replacing eight screws.

Testing the memory

Verifying the memory is recognized

The first thing was to boot up and choose About This Mac to verify that the system recognized the memory. The Memory description will vary, depending on the type of memory (depends on the MacBook Pro model you’re using).

Stress test

The 64-bit MemoryTester program run-stress-test command stresses the computer maximally. There is nothing that can stress it more; it keeps all CPU cores at 100% while relentlessly writing and reading memory (disk I/O on all disks is optional). Without a doubt, 99.99% of MacBook Pro users will never stress their machines this hard! The stress test generates maximum heat, the killer of marginal components, and a sure way to cause system crashes with “weak” parts.

A fully “stressed” MacBook Pro (2 cores)

After three hours of this abuse, the system actually seemed cooler than under lighter loads with the module it replaced! That is subjective (not measured), but was a very pleasant surprise that bodes well for long-term reliability.

My MacBook Pro has been rock solid since installing the 4GB module, OWC has succeeded at producing a “first” for laptops in breaking the 4GB barrier.

In use

In day-to-day use in a variety of tasks, I experienced no unusual events whatsoever—no indication of anything unstable or unusual. This was true of both the 2007 MacBook Pro 2.4GHz and the late 2008 unibody MacBook Pro 2.8GHz.

The greatly enhanced Photoshop performance should draw the attention of anyone working with large image files; a wide battery of benchmarking was done with the module installed.

UPDATE: the 4GB module for prior-generation (pre-unibody) MacBook Pros has dropped in price to $159 as of February 2009. Now it’s a no-brainer upgrade!

Pricing on the DDR3 memory for the 2008 unibody model is more, but it also has come down in price.

I emailed Lawrence O’Conner at OWC about the great results I was seeing, but mainly I wanted to know why the 4GB module cost so much more (per GB) than the 2GB modules. He responded:

They are the latest, top tier parts - that are able to use less power and run cool in the system as to provide reliable operation under load. Nearly two years it's taken for this density module to be possible in terms of the cool running chips to be available - prior stuff and other stuff out there way overheats and causes lockups by comparison.

Editor’s note: the latest and greatest memory (1066MHz DDR3) is also quite a bit more expensive than the older 667MHz DDR2 memory, and sadly the premium offers very poor value in terms of performance, a few percent for most tasks.


Other World Computing has a great product on their hands: a 4GB memory module that allows upgrading to a total of 6GB memory with absolutely trouble-free operation, even under severe load (MemoryTester).

For those needing a performance boost for the MacBook Pro (late 2008 unibody or previous models) related to adequate memory, the value proposition is unbeatable, and the Photoshop results prove it. Especially when working with large files in Photoshop, the system is much more responsive.

The benefits go beyond Photoshop—the extra memory allows the system to cache far more than it otherwise could, which means that an application, once launched, is likely to stay in the cache, making a 2nd launch far faster. Ditto for files, and the ability to run a “serious” set of programs simultaneously. Overall system response is thus enhanced in general.

If you already have 4GB (2X2GB), then get the 4GB module alone. If you have 2GB (1X1GB), then get the 6GB kit (it’s only slightly more than the 4GB module alone).

See also the review of the Apple MacBook Pro “unibody” 2.8GHz.

Where to buy

Click to read about the OWC test lab

Get it at Other World Computing.

OWC maintains a testing lab with every Mac they selling memory for, so they can guarantee it works in your Mac.


Click to view memory
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