My DIMM Riser A (Mac Pro) has 'Disappeared'!

Discussion in 'Mac Pro' started by spetznatz, Jan 29, 2009.

  1. spetznatz macrumors regular

    Joined:
    Jan 5, 2006
    #1
    Just bought 4 x 2GB modules, installed them on both risers, in the first two slots.Remaining slots are filled with 4 x 1 GBs.

    Restarting, check 'About This Mac...' it reports 6 GB instead of 12 GB.

    Using ASP, it reports that DIMM Riser A 'Empty' for every slot.

    I've re-seated the riser, same thing. I noticed that the red LEDs flashed on both risers when I started up...so both are getting juice.

    Anyone have any idea what's going on?

    TIA,
     
  2. Consultant macrumors G5

    Consultant

    Joined:
    Jun 27, 2007
    #2
    Rotate the risers and see whether it works.

    Remove all ram.
    Try a different pair at a time.
     
  3. NATO macrumors 68000

    NATO

    Joined:
    Feb 14, 2005
    Location:
    Northern Ireland
    #3
    That happened to me once. Try restarting and holding down Cmd+Alt+P+R when it 'bongs', keep that held down until it 'bongs' again. Let me know if that works :)
     
  4. spetznatz thread starter macrumors regular

    Joined:
    Jan 5, 2006
    #4
    Cheers, both --

    I'm going to run Apple Hardware Test on it as well...

    Apparently, if the red LEDs stay on, the riser is buggered -- that's not the case here, though.
     
  5. NATO macrumors 68000

    NATO

    Joined:
    Feb 14, 2005
    Location:
    Northern Ireland
  6. spetznatz thread starter macrumors regular

    Joined:
    Jan 5, 2006
    #6
    Well, I ran Apple Hardware Test, -- it said there was nothing wrong.

    However, swapping the risers around, ASP reports that Riser B is now empty, so it looks like the riser is hosed.

    Damn.
     
  7. spetznatz thread starter macrumors regular

    Joined:
    Jan 5, 2006
    #7
    Wow, weirder and weirder.

    I put all the 2 GBs on the 'good' riser, all the 1 GBs on the 'bad' riser.

    Put both risers back in...

    I now have 12 GBs...:confused:
     
  8. OrangeSVTguy macrumors 601

    OrangeSVTguy

    Joined:
    Sep 16, 2007
    Location:
    Northeastern Ohio
    #8
    Looks like you were pairing the memory wrong?
     
  9. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #9
    That, or the DIMM's weren't fully seated. ;)
     
  10. spetznatz thread starter macrumors regular

    Joined:
    Jan 5, 2006
    #10
    But the dual-channel operation requires that the first slots on the risers be filled with the highest-capacity DIMMs...doesn't it? So it should be 2.2.1.1 on both risers.

    I can't see that the DIMMs were improperly seated... they all locked in as they were supposed to...
     
  11. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #11
    I've had instances where I thought the DIMM was properly seated, and they locked. They were located in the correct slots. But like this situation, weren't read. The lock was sort of stiff/tight, BTW. Not make me think they wouldn't have worked, but that turned out to be the case.

    Re-seating did the trick. ;) At least it was something simple, rather than a bad riser or DOA memory. :)
     
  12. rylin macrumors 6502

    Joined:
    Aug 18, 2006
    #12
    Take them out and spin them clockwise?
    Now that's some serious voodoo! :D
     
  13. Trip.Tucker Guest

    Joined:
    Mar 13, 2008
    #13
    You misread the sentence. He means swap the boards over, also worded as rotate the boards. If you haven't worked as an engineer you would not understand that term....which you clearly didn't.
     
  14. nanofrog macrumors G4

    Joined:
    May 6, 2008
    #14
    Given the last sentence, I thought he was joking. :)
     
  15. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #15
    Clearly....

    I don't not why you would have to work as an "engineer" to know that "rotating" the boards meant swap the board positions. Oh well....

    S-
     

Share This Page