RAM: 2gb + 1gb ?

Discussion in 'Mac Basics and Help' started by ahm, Feb 19, 2009.

  1. ahm macrumors member

    Feb 14, 2009
    I hastily ordered a 2gb memory stick to add to my new aluminum Macbook... but recently came across some discussion about mixing RAM. The discussion was about adding 6gb (4gb + 2gb). Someone said you would lose performance because the RAM doesn't match and mentioned something about dual channel.

    I read a little about dual channel, but I was wondering if I combine a 2gb stick with a 1gb, will I really utilize the 3gb of memory?
  2. CalumC macrumors regular

    Oct 15, 2008
    Leeds, UK
    I don't know the exact tech behind it, but 3gb will run faster than 2gb, but not as efficiently at certain things. Something like that. Incidentally, i have 2 + 1 in my polybook, works well but it wasn't by my choice, upgraded by previous owner. Will move to 4gb soon.
  3. zPolarBear macrumors newbie

    Feb 18, 2009
    One thing I remember reading was the suggestion that both sticks use the same timing CL (CAS Latency, etc)...
    It is usually written on the sticks or on the packaging.

    The 2G sticks I bought for the MacBook read: 256Mx64, 128Mx8/DDR2 667/ 5-5-5

    It's the 5-5-5 I am referring to.

    The post also said not to mix DDR 667 with DDR 800 or 556 or what ever the other numbers are...

    The 1G modules I removed are: PC2-5300S-555-12, probably also 5-5-5, so these sticks would probably play well together if PC2-5300 and DDR 667 mean the same thing...
  4. ahm thread starter macrumors member

    Feb 14, 2009
    I'm just replying because I have an update. Just in case anyone else is wondering the same thing at some point... maybe they'll come across this thread in a search or something.

    Anyway, from what I've been reading, it doesn't matter if they're different sizes. But, I think it was something like, if you mix 667mhz and 800mhz, both will clock down to 667mhz.

    If anyone can provide some facts based on actual knowledge, that would be cool.

    Besides that, I added that 2gb module just now. I timed my startup before and after, and there is about a 12 second difference. System Profile recognizes the RAM just fine and I ran a hardware test. All is good so far. It's nice to have that extra 2.22gb of room. I'm looking forward to running Virtualbox with the extra RAM as well. I'll buy another 2gb sooner or later, it's pretty cheap (Crucial).

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