Problem with early 08 Mac Pro

Discussion in 'Mac Pro' started by OH Mac Fan, Mar 8, 2013.

  1. OH Mac Fan macrumors newbie

    Joined:
    Jul 21, 2011
    #1
    A week or two ago my Mac just restarted on its own twice and was then running slower than I've ever seen it run. I checked the system preferences and it listed only 2GB of RAM [I had 4]. I have a red light on DIMM 1 on my lower riser card so I thought it might be the ram. I bought another 4 GB of ram... same problem. I tried different orders a single pair (new ram only), double pair, I tried everything. With two pair (2x4) in it would read 4GB but says the lower card is empty. I went ahead and bought another riser card to replace the lower one with the red light on it... same problem. Please tell me it's not the logic board and I'm missing something. I can't afford $800 to replace the logic board. :(
     
  2. djjclark macrumors regular

    Joined:
    Feb 17, 2008
    #2
    well you are mostly proving it is the LB or connector. move the top riser down and see if the light stays on the bottom. If out of three risers and several ram chips the problem always stays on the bottom I would look to make sure the connector is clean (vacuum and air compressor) and no debris is in it.
     
  3. OH Mac Fan thread starter macrumors newbie

    Joined:
    Jul 21, 2011
    #3
    Ok, now I'm really stumped. I checked for debris... good to go there. I had the old board in the upper slot and the new board in the lower slot. I flipped the boards, now I get a red light on the new upper board :mad:

    I thought... ok, maybe by some curse I got bad new ram. I swapped the ram positions on both boards leaving the new (former) lower on the top and the other board on the bottom. Same problem. I'm stumped.
     
  4. Brian Y macrumors 68040

    Joined:
    Oct 21, 2012
    #4
    You basically need to try every single combination to see where the problem lies:

    - top ram in top board, bottom ram in bottom board
    - bottom ram in top board, top ram in bottom board
    - both of the above with the boards switched positions
    - all 4 of the above with one stick of RAM in each board
    - all of the above with different sticks in the slot

    If that doesn't work, then it's going to be the backplane board.
     
  5. Tesselator, Mar 8, 2013
    Last edited: Mar 8, 2013

    Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
    Location:
    Japan
    #5
    Yeah, those RAM Riser boards aren't a real smart design IMO. Probably due to the component grade selected for the line assembly. I had a similar issue with a 2006 MP myself. Many times when removing and reinstalling those riser boards for cleaning, testing RAM, or whatever, the initial first few cold starts would produce red lights and the system wouldn't recognize the RAM on that card. 1 to 3 reseats later and it's all good. This tells me that the parts used (probably the card thickness and the mainboard headers) are NOT of optimal quality and/or tolerance levels.

    To clean the landings on the mainboard's headers use acetone and a cotton ear swab. lightly (and I really mean lightly) dampen the swab in pure acetone. Place it between two of the landing surfaces and rotate R&L a few times. Repeat for about 3 or 4 landing sets and then grab a new swab even if it doesn't look dirty.

    When done examine the card edge connector on the riser board itself. If you see any scratches or marks at all get yourself a pink pencil eraser (not the white rubber ones) and rub down those contacts. Apply about the same pressure you would when erasing pencil marks off paper - assuming you weren't one of those kids who constantly turning in papers with eraser holes in the paper. :) When done use a tissue paper and some of that acetone and wipe down the card edges with it.

    Reassemble and have a go. You might even still need to reseat the card once or twice. If that doesn't fix it then I would move to RAM testing before considering a mainboard replacement!

    Assumming you have 8-cores The fastest way to actually test for bad memory beyond Apple's initial check, is to download Rember, duplicate it the number of times you have CPUs (one copy per core), open one and enter RAM/Cores (8GB ÷ 8?), set that much minus about 5MB in the setting window, turn OFF "Continue on error" and set "Quit All Apps" and "Quit Finder" in the preferences, quit and then open all 8 instances (which should now all use those settings), and then just start them off. If it appears to be chugging too slowly or if one Rember instance seems almost stuck, stop (don't quit) that one and give it less RAM to do - a little at a time till it takes off normally.

    When you test the memory use Apple's default SMC system cooling profiles. If you have SMCFanControl installed set it to the installation preset called Default - which will allow Apple to have their way and let the RAM heat up to their idea of operating temperatures - which is better when testing for bad memory. ;)
     
  6. OH Mac Fan, Mar 8, 2013
    Last edited: Mar 8, 2013

    OH Mac Fan thread starter macrumors newbie

    Joined:
    Jul 21, 2011
    #6
    Alright, I finally got it licked. One of the old ram sticks went bad. Depending on where the ram was inserted it would cause it to show either that stick failing (the old ram) or the stick it paired to (the new ram). In some configurations, if that was the first stick or in the first pair, it wouldn't even boot. At least it's not the motherboard. What a pain :mad:

    ETA
    I went ahead and ordered another new set for 8GB total and I'm just going to trash this Corsair ram before the other stick fails.
     
  7. Tesselator macrumors 601

    Tesselator

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    Jan 9, 2008
    Location:
    Japan
    #7
    Yep, it's a pain. Glad you got it sorted tho!
     
  8. OH Mac Fan thread starter macrumors newbie

    Joined:
    Jul 21, 2011
    #8
    Thanks for the tip, but when the system doesn't acknowledge the ram's there you can't test it ;)

    ----------

    Thanks and thanks for the help everyone. :D
     
  9. snberk103 macrumors 603

    Joined:
    Oct 22, 2007
    Location:
    An Island in the Salish Sea
    #9
    Just reading through this thread... and thought "I had exactly the same problem" and was going to tell you to really test the RAM. The store I took my Mac Pro (2008 8-core as well) was just getting ready to order a new riser card because swapping the RAM around was giving inconsistent results - pointing at the riser card. However, a really deep test of the RAM showed it to be RAM after all.

    So, while this is no longer relevant for you (Yay! for the cheap fix, eh?!)... for the next person with a 2008 and weird RAM errors... be very very sure it isn't a bad stick of RAM before concluding it's a bad riser or logic board. This seems to be a not-uncommon issue.
     
  10. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
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    Japan
    #10
    Of course. :D You'd have to place it where it's recognized. ;P

    Hehe...
     
  11. MacVidCards Suspended

    Joined:
    Nov 17, 2008
    Location:
    Hollywood, CA
    #11
    Somewhere on this board is a recent thread that I started where I was trying to figure out which 8GB sticks actually worked in a 2008.

    WHat I never mentioned was that one of my risers became convinced that ANY RAM put in it was bad after the non-compatable 8GB sticks were tried. The red lights were on and regular old 2 Gb or 4GB sticks were invisible.

    I tried resetting SMC, etc and still the riser seemed like it had been ruined by the 8GB sticks.

    Then, it started working again after a few re-boots.

    Not sure how or why.

    But that was part of why I was trying to get people who have found actual working 8GB sticks to post the part numbers and specs so that we could figure out what works.
     
  12. Tesselator macrumors 601

    Tesselator

    Joined:
    Jan 9, 2008
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    Japan
    #12
    That sounds like it would be related to the 1st paragraph in post 5 somehow or another.
     
  13. TheEasterBunny macrumors 6502

    Joined:
    Jan 22, 2013
    Location:
    Delaware
    #13
    Side Note

    Acetone can also dissolve the coating on the boards be very careful, also some cotton swabs are not made of cotton. Some are made of polyester, acetone will dissolve polyester as well. Once the acetone has evaporated it creates this semi-hardened coating which can be hard to remove.
    I prefer to use heavy card stock (made of paper) dipped in acetone for slots, any paper bits left behind can be removed with air after drying.
    Just my .02
     
  14. DPUser macrumors 6502a

    Joined:
    Jan 17, 2012
    #14
    Look into Caig products (DeOxit, etc) for connector and potentiometer cleaning/optimization. I have used Caig ProGold (now known as DeOxit Gold) extensively with consistently fantastic, long-lasting results.
     

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