Can I replace a DDR2 RAM module with a DDR3 module?

Simon P September 17, 2013
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The computer is a Compaq Presario CQ40. It currently has 1 GB of RAM DDR2 (Samsung-manufactured). There are two slots in the RAM part.
It says 766 MB usable ( which I think is because part of it goes to being the graphics card). The processor is an AMD Sempron(tm) SI-42 2.10 GHz.
I wanted to upgrade the RAM to 2 GB with a new installation of one 1 GB RAM, but I was also wondering if I can replace the old 1 GB DDR2 with a new 2 GB DDR3 RAM, and add
one more 1 GB DDR3 RAM, making the whole RAM capacity to 4 GB DDR3.
Please give me some thoughts. I think there have to be compatibility between the
motherboard and the new planned DDR3 RAMs as well, which I am not sure how to check.

  1. Dalsan M
    September 18, 2013 at 6:56 pm

    Another thing to note is that the pin placement is different between each iteration of DDR memory. Unless the motherboard supports both DDR2 and DDR3, upgrading to DDR3 will not work. Here is where you can get more information: If the computer was a desktop, I would say unless you wish to upgrade the motherboard, stick with DDR2. The cost and effort it takes to just upgrade the motherboard so you can use DDR3 along with your existing processor and hard drive is not worth it, mostly since the performance gain may not be that big of a difference to really notice. Since this is a laptop, you would not be able to upgrade the motherboard, so you would be stuck with DDR2.

  2. Saumyakanta S
    September 18, 2013 at 3:36 pm

    yep , Oron is right , DDR2 and DDR3 are different technologies and the motherboard may not be compatible with DDR3 RAM , So just consult it with your motherboard manufacturer.

  3. Oron J
    September 17, 2013 at 1:02 pm

    You cannot change DDR2 modules for DDR3, they are different technologies and the modules are not compatible with each other.

    According to Crucial you can upgrade your laptop either to 4GB or to 8GB, depending on the exact model. I suggest you head over to Crucial's site ( in the US, in hte UK, and I'm sure there are other local versions) and run the "system scanner" which will identify your model accurately, and will take you to a page showing you all the upgrade options available (available from them, that is, but they have a fairly comprehensive stock of memory modules).

  4. Hovsep A
    September 17, 2013 at 12:00 pm

    According to the manual
    1) 2 SODIMM slots
    2) Supports up to 4 GB of system RAM
    3) PC2-6400 800-MHz, DDR2
    4) Supports the following configurations:
    ? 4096 MB total system memory (2048 × 2)
    ? 3072 MB total system memory (2048 + 1024)
    ? 2048 MB total system memory (2048 × 1)
    ? 2048 MB total system memory (1024 × 2)
    ? 1024 MB total system memory (1024 × 1)

    if you change to DDR3 you will have problems