Is this RAM compatible with my late 2008 Macbook Pro?

The RAM on Amazon will NOT work. It is slower that what your computer is rated. Note in MacTracker that they show the proper RAM speeds:

Yours needs PC3 8500; the Amazon RAM is PC2 5300 for Late 2007 and Early 2008 MBPs. Go with the Crucial site or Other World Computing:

http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade/DDR3

Exactly which late 2008 MBP do you have? A 15", Unibody Model identifier 5.1 or a 17" non-Unibody Model Identifier 4.1. The former takes the higher frequency RAM (1066 MHz) and the latter takes the lower frequency RAM (667 MHz).

The Unibody model can accept 8 GB RAM, the non-Unibody can accept 6 GB RAM.

Ciao.

RAM you get must be designated for your age and type of model in question. Getting a specific timing such as

"....PC3 8500; the Amazon RAM is PC2 5300" is insufficient to guarantee compatibility. First identify exactly what model you have according to Apple, then buy RAM from a vendor that says the RAM is for the age of model in question. Here are tools to find your model and model age:

https://discussions.apple.com/docs/DOC-6413

And three vendors that sell by the age/model:

http://www.datamem.com/http://www.crucial.com/http://www.macsales.com/

There may be others. Do not buy valueRAM or any RAM without a lifetime warranty.

Enter your MBP serial number here and post back the model information:

https://selfsolve.apple.com/agreementWarrantyDynamic.do

In order to give you accurate advice, this information is necessary.

Ciao.

Yes, that shows the RAM I linked in my first post is what you need. The others rightly mentioned something I'd overlooked--the 17-inch MBP did not change to the Unibody form factor until well after the 15-incher. However, yours is Unibody and uses PC3-8500 (1066mhz) RAM.

Yes, this confirms that Allan Jones has provided you with accurate information. The RAM that you selected does not conform to the specifications required for your MBP. Examine his post for the correct specifications and the best vendors for Mac compatible RAM.

Ciao.

You can have mismatched sizes but you will get best performance with matching sizes.

You may keep the existing 2 GB RAM module and add a 2 GB or 4 GB module. Both will work. The more RAM that you install, the more efficient the MBP will run even if the modules are not the same capacity.

Matched pairs are best, but mismatches will work, just not as well for the same amount of given RAM.

Ciao.

You can leave the 2GB module that is already there.

However, my experience with MacBook Pros goes back to 2007 and all I've seen or worked on had both slots occupied when shipped from Apple. Even the very early MBPs that shipped with only 1GB RAM had two 512MB modules. My Late 2007 MBP shipped with 2GB RAM total--two 1GB modules. My 2012 MBP shipped with 4GB--two 2GB modules.

So I'm wondering why there is an empty slot now. Please do this:

1) Click and hold on your Apple menu, then press OPTION to change the first entry from "About this Mac" to "System Information" (or "System Profiler" on older Mac OSX versions).

2) When System Information/Profiler opens, select "Memory" from the left-hand Contents Pane. You get this:

Does the upper section of the main pane show both slots are occupied? If so, what RAM sizes are shown?

Allan, just as a point of information, my 2006 MBP came with one 1 GB RAM module. I did order a second third party 1 GB RAM module to max it out.

At the time you could have it with it with one 512 KB RAM module, two 512 KB ram modules, 1 GB RAM module.

This said, it may have been the case with only the very early MBPs.

Ciao.