I've started virtualizing Windows 7 on my Mac and I've realized 4GB of ram simply isn't enough for listening to music, surfing the web, virtualizing Windows, and running a compiler all at once.

The first thing I did was look on Apple's site and see what specs I needed to look for..I bought my iMac in the spring of last year so the specs for new ram are as follows: 1333MHz DDR3 (PC3-10600)

So I read that and thought, okay, and then I read their price, $ 200.00 for just 4 GB. Wait a second, maybe a little out of my price range. Then I hit up sites such as NewEgg, and found some pretty good deals; however, I found that some of them were labeled SDRAM and some SO-DIMM, and I guess my question to you folks is: What are the differences between SDRAM and SO-DIMM RAM, and which should I use for my iMac?

2 Answers 2


You're getting your terminologies mixed up.

SDRAM (Synchronous Dynamic Random Access Memory) is just the type of RAM on a DIMM. In your case as you've stated it's DDR3 (3rd generation of Double Data Rate)

A DIMM is a standard format Dual In-line Memory Module. These have different pins for the different types of memory specification, so a DDR3 module will have a different edge connector to a DDR2 module and so on. A SO-DIMM is a Small Outline version of a DIMM, hence the "SO". These were designed for laptops where full size DIMMs wouldn't fit.

Apple use SO-DIMMs in their iMacs now, so DDR3 PC3-10600 (10600 is the peak transfer rate, so going lower than this will be a bad thing for performance) SO-DIMMs are what you want to get.

  • Thanks man, really appreciate you taking the time with my question.
    – Jerrod
    May 11, 2012 at 17:54

QUOTE FROM MAC BOOK PRO LATE 2011 Installing Additional Memory Your computer has two memory slots that you access by removing the bottom case. Your MacBook Pro comes with a minimum of 4 gigabytes (GB) of 1333 MHz Double Data Rate (DDR3) Synchronous Dynamic Random-Access Memory (SDRAM) installed.

Each memory slot can accept an SDRAM module that meets the following specifications:

  • Double Data Rate Small Outline Dual Inline Memory Module (DDR3)
  • format 30 mm (1.18 inches) 204-pin
  • 2 GB or 4 GB
  • PC3-10600S DDR3 1333MHz Type RAM

You can add two 4 GB memory modules for a maximum of 8 GB of memory. For best performance, fill both memory slots and install an identical memory module in each slot.

To install memory in your MacBook Pro: 1 Follow steps 1 and 2 beginning on page 37 to remove the bottom case. Important: When you remove the bottom case, you expose sensitive internal components, which can be affected by static electricity. 2 Before touching the memory assembly, discharge any static electricity from your body by touching a metal surface inside the computer.

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