2GBx2 memory upgrade for intel imac doesn't work

Discussion in 'Mac Basics and Help' started by guywholikesmacs, Dec 27, 2009.

  1. guywholikesmacs macrumors newbie

    Joined:
    Dec 27, 2009
    #1
    i've seen this problem posted by other people with different macs than mine and i just wanted to see if i have the same problem or not.

    i got two 2GB memory modules as a gift (crucial brand 200-pin ddr2 sodimm pc2-6400 cl6) for my mid 2007 2.4ghz intel core 2 duo 20" imac (i don't know which chipset that is). the memory will not work when i put both modules in. the comp will start but wont get past the black screen.

    when i put EITHER of the new modules in with the old 1GB module IN EITHER SLOT, it works. so i know it's not bad memory and i know i dont have a bad memory slot (right?).

    as ive said, i have read that this is an issue with the memory bus speed, but i am fairly certain that the memory i received is the correct bus speed (667mhz) for the computer that i own.

    any help would be greatly appreciated.
     
  2. spinnerlys Guest

    spinnerlys

    Joined:
    Sep 7, 2008
    Location:
    forlod bygningen
    #2
    According to EveryMac, your iMac has a bus and memory clock speed of 667MHz, the RAM you bought has 800MHz.
    PC2-5300 DDR2 vs. pc2-6400
    5400/8 = 667 , 6400/8 = 800
     
  3. guywholikesmacs thread starter macrumors newbie

    Joined:
    Dec 27, 2009
    #3
    so, would my system profiler be telling me the new memory module is 667 because thats what it is down-converting it to?
     
  4. spinnerlys Guest

    spinnerlys

    Joined:
    Sep 7, 2008
    Location:
    forlod bygningen
    #4
    I don't know if System Profile would do such a thing, but your Mac is not capable of identifying that the RAM you gave it has more speed than it can accept.

    Does your Mac show that you have 3GB RAM when you have the old 1GB and the new 2GB module inserted?
     
  5. guywholikesmacs thread starter macrumors newbie

    Joined:
    Dec 27, 2009
    #5
    yes, it does show 3GB or RAM with the one old and the one new.
     
  6. Guiyon macrumors 6502a

    Joined:
    Mar 19, 2008
    Location:
    North Shore, MA
    #6
    Rarely the case. Most properly programmed SPDs on DIMMs should allow for down-clocking; only the really cheap ones usually have issues (and I have only run into 1 or 2 of these).
     
  7. Nano2k macrumors regular

    Joined:
    Nov 6, 2009
    Location:
    Europe
    #7
    Some ram sticks are just not compatible with certain motherboard/chipsets, it's possible that when you put the 1Gb and 2Gb stick in, the computer gets the ram timings of the 1Gb stick which also are compatible with the 2Gb stick, but when you put 2x2Gb sticks it cannot read/find the proper timings or the timings it reads cause the computer to hang.

    Looks like you will have to choose another brand.
     

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