Last Gen White iMac - Still limited to 3GB?

Discussion in 'iMac' started by sigamy, Feb 1, 2008.

  1. sigamy macrumors 65816

    Mar 7, 2003
    NJ USA
    Just wanted to put a final nail in the coffin on this...I currently have two 1gb modules in my 20" 2.16Ghz C2D iMac (the last white iMacs).

    From what I've read, if I add two 2gb modules, the system will only be able to access 3gb. Is this still correct?

    If it is correct, should I just install one 2gb module + one 1GB for a total of 3gb? Or should I go with matching pairs and install two 2gbs? How much of a speed difference will there be?
  2. roland.g macrumors 603


    Apr 11, 2005
    One mile up and soaring
    3GB is better performance than 2GB matched. The matched vs. unmatched doesn't matter as much as the total amount. Actually you will get 3.2 if you put in 4GB b/c that is all the chipset can address. It wasn't until the Santa Rosa chipset that 4GB was available. 3 would be your best bet. Don't worry about putting in 4. You could also stay with 2 if you wanted and be fine.
  3. neiltc13 macrumors 68040


    May 27, 2006
    Not really sure where this sudden desire for everyone to have 4GB RAM comes from. I use 2GB and find that even this is excessive.
  4. eXan macrumors 601


    Jan 10, 2005
    Me too :confused:

    It seems like everyone at macrumors is getting 4 GBs installed in their MacBooks and iMacs. What for?

    I barely hit the 1 GB limit on my MacBook doing web/mail/chat/itunes/pages/word + h.264encoding and my Page Outs rarely exceed 200-300 MBs.

    iMac G5 has 1.5 GBs and I'm using Aperture on it with Photoshop to edit 8 MP photos, but its more limited by its slow CPU than amount of RAM (I checked Activity Monitor while doing doing my usual stuff in those 2 apps and RAM was just almost filled)
  5. OllyW Moderator


    Staff Member

    Oct 11, 2005
    The Black Country, England
    2GB RAM chips have dropped in price recently, on Crucial UK last week they were only £10 more expensive than 1GB so they are no longer an expensive option.

    I've got 4GB in my mini, only accessing 3.3GB but with the slight advantages of dual channel memory (which works better with graphics that use shared RAM).

    More info here.
  6. Leon Kowalski macrumors 6502a

    Leon Kowalski

    Sep 20, 2007
    Gondwanaland Reunification Front HQ
    1) The OS-X filesystem uses all available "idle" memory for disk buffer-cache.
    This can greatly improve the performance of many apps by avoiding Page Ins
    when re-reading "disk data" that's already resident in "inactive" RAM. Thus,
    adding memory does improve performance -- even when there's more than
    enough to prevent Page Outs.

    2) Independent of Page In/Page Out considerations, a "matched pair" of memory
    modules yields a 5%-ish improvement in overall performance. So, "wasting" $50
    or so for a second 2GB module is a huge bargain -- compared to "investing" $250
    in a 2.4 GHz to 2.8 GHz CPU upgrade (which yields only a 10%-ish improvement
    in overall performance).

  7. gorby macrumors 6502

    Oct 20, 2007
    You will still get better performance from 4GB matched in a white iMac.

    Look at the benchmarks from OWC:

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