Help with OWC RAM in my Mac Pro.

Discussion in 'Mac Pro' started by luka, Jun 24, 2008.

  1. luka macrumors member

    Joined:
    Jan 13, 2008
    #1
    I'm the owner of a new mac pro, and I recently bought 4gig of ram from OWC. I installed the ram correctly - two gigs per stick, shuffled the old ram down to the second slots installed the new ram in the first slot on the top and bottom.

    However, the mac's only recognizing the new 4 gigs in the first slot. I was pretty static safe, touching my case in all the right places every few minutes and not moving. I'm pretty sure I haven't killed anything.

    Any idea what could be wrong? Is there some little bite of common knowledge someone is keen to share?
     
  2. richard.mac macrumors 603

    richard.mac

    Joined:
    Feb 2, 2007
    Location:
    51.50024, -0.12662
    #2
    a few things to consider.

    have you installed the FB_DIMMS correctly? from the Mac Pro service guide:

    Screencapture 1.jpg

    the RAM may be faulty so run the Hardware diagnostic test by booting into the first install DVD while holding D.
     
  3. rikoshay macrumors member

    rikoshay

    Joined:
    Mar 28, 2006
    Location:
    No. California (in the Redwoods)
    #3
    I've seen this before, with new RAM, & recently with my Mac Pro. A cure can be to really clean the plug contacts on each DIMM. Clean all contacts with alcohol, & use a pencil eraser to make them shiny. Then, plug them in & remove them. Repeat the plugging-in a few times to guarantee connection with all the pins. Good luck.
     
  4. luka thread starter macrumors member

    Joined:
    Jan 13, 2008
    #4
    I've got 6GB now, I moved the two OWC modules to raiser b instead of having one above, one below. To my understanding, it's not how the apple manual said it should be done, no? ie, the manual states that the setup should be
    Raiser A:
    OWC 2gb
    AppleRAM 1gb

    Raiser B:
    OWC 2gb
    AppleRAM 1gb


    However, I've got it set up as
    Raiser A:
    Apple
    Apple

    Raiser B:
    OWC
    OWC

    what the...?
     
  5. Roy macrumors 6502

    Joined:
    Jul 6, 2006
    #5
    I don't know what manual you are reading, but when I go to Apple's website and look at the Mac Pro early 2008 manual, it shows you are to install it the way you have it installed now. I don't see anywhere where it states to install it the way you originally installed it.

    On the bottom memory card, open the ejectors on the DIMM slot and push them out
    to the sides, and then remove the DIMM from slot 1.
    Important: When installing or removing DIMMs, don’t touch the gold connectors on
    the DIMMs or the memory cards.
    4 Reinstall the DIMM you removed on the top memory card by aligning it in DIMM slot 2,
    as shown in the illustration, and pushing both ends of the DIMM down until the tabs
    are vertical and the ejectors snap into place.
    5 Install the first pair of additional DIMMs on the bottom memory card in DIMM slots 1
    and 2, the slots closest to the card’s gold connectors.
    Important: Always install DIMMs as matched pairs and in the order shown here.
     
  6. sickmacdoc macrumors 68020

    sickmacdoc

    Joined:
    Jun 14, 2008
    Location:
    New Hampshire
    #6
    As the documentation Roy quoted above states, pairs in any single riser must be matched capacity. From what I can determine from your "experiments" your current setup would have a 2GB Apple chip in the same riser with a 1Gb Apple chip, in which case only the one in the first slot will be recognized because of the unmatched pair.

    Also as he noted, the matched pairs in a single riser is for the MacPros introduced in Jan. 08. The previous generation MacPros had a different method of addressing memory more along the lines of what you were describing originally (2+1 in each riser).

    It would probably help if you defined exactly what memory sticks you currently have in hand to work with and we can help you more. It seems from your notes that you may have 2x2Gb OWC sticks, 1x2Gb Apple stick and 1x1Gb Apple stick, but some of your other "experiments" show 3 OWC sticks and only 1 Apple stick, so you can see where some of our confusion comes from.

    Make sure you are reading documentation concerning the correct generation of your MacPro also- will avoid a lot of confusion.
     
  7. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #7
    Gaak. No.

    Both the older and the newer MacPro require RAM to be installed in pairs, on the same riser. Populate your slots, starting with the largest RAM pair, in this order

    A1
    A2

    B1
    B2

    A3
    A4

    B3
    B4

    The 2008 MacPros ship with the Apple RAM in the A1 B1 positions, this is NOT to be maintained when you add more RAM. Move the Apple module from A1 to B2

    To the OP:
    First make sure you have the OWC RAM in A1 A2 and the Apple in B1 B2

    Do you have a red LED shining on either of the memory riser cards?

    What happens if you swap cards between the card sockets?

    (Always shut the machine completely off when moving memory or risers)
     
  8. Roy macrumors 6502

    Joined:
    Jul 6, 2006
    #8
    CanadaRAM,

    Can you explain, in "simpleton terms", why the 2006 Mac Pro and the 2008 Mac Pro ship (shipped for 2006) with the 2 memory sticks in 2 different ways? Always wondered about that one.


    I would also like to know if swapping the cards placement would make any difference or is it really possible to swap the cards placement.
     
  9. CanadaRAM macrumors G5

    CanadaRAM

    Joined:
    Oct 11, 2004
    Location:
    On the Left Coast - Victoria BC Canada
    #9




    Because that's the way Apple does it?

    The two risers are identical and can be swapped between the 2 positions.
     
  10. Roy macrumors 6502

    Joined:
    Jul 6, 2006
    #10
    Well, I did ask for the Simpleton explanation.:)
     

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