mac pro won't recognize memory... sometimes, arrgh

Discussion in 'Mac Pro' started by loblah, Dec 22, 2008.

  1. loblah macrumors newbie

    Feb 20, 2008
    i have a Mac Pro Quad Xeon/8-Core, it came with 2gb RAM, less than a year old

    i bought 2 x 2gb of apple qualified ram from OWC, this is from the invoice:

    OWC 4GB Mac Pro 800MHz Kit 2GB x 2 FB
    Matched Modules 2.0GB per for Mac Pro Quad Xeon/8-Core Qualified with Apple Qualified Heat-Spreader. LifeTime Advance Replacement Warranty.
    OWC64FBMP2GB 2GB Mac Pro Qualified FB-DIMM 800MHz ECC

    here's the thing....

    SOMETIMES (when booted up) the computer recognizes all the RAM in the machine, 6 GB

    SOMETIMES the computer only recognizes the ORIGINAL 2 GB of RAM

    and SOMETIMES the computer only recognizes the new 4 GB of RAM, and not the original 2 gb

    YES, the RAM has been installed correctly (i think), the original 2 x 1GB sticks are in the top tray, the newer 2 x 2GB sticks are directly below in the bottom tray

    is it the RAM?

    is it the COMPUTER?

    is it ME?

    All I want for Xmas is my 6 gigs of RAM.

  2. ObaMaciden macrumors member


    Nov 4, 2008
    I'm having the same issue.

    I have 8x 2GB OWC RAM. It shows the Dimm Riser B as "empty" in slots 1 and 2, doesn't matter if I switched the RAM boards. This was first noticed after I installed the combo 10.5.6 update last week.:(

    At first I physically reinstalled each RAM and it went back to 16 GB. Now it's back to 12 GB again.

    I'm calling Apple to find out what's up. I know there are issues with the recent update. Hopefully this won't consume too much time!!

    Any help will be greatly appreciated.:D
  3. sternla macrumors newbie

    Dec 23, 2008
    mac pro ram

    I manage a large number of macs including several mac pros. I ran into this issue. The thing that seemed to fix it for me was playing with the order the ram is installed. For me, the problem occurred when I had different size ram modules within the same pair of banks. You have 8 slots, 2 riser cards, 4 banks. Ram has to be added in pairs. Try swapping the order of larger ram vs smaller ram, but be sure to keep the ram in identical size within bank. Hope that makes sense. If possible do same size ram in banks 1-2 and 3-4.
  4. ObaMaciden macrumors member


    Nov 4, 2008
    I just finished trouble-shooting and determined that one of my 2GB sticks is dead. A simple clue: The LED light on the lower Riser (B) was on Dimm 1. Just to be sure, I reset PRAM to no avail.

    To determine whether it was RAM Riser board or RAM error, I put in the original Apple 1GB sticks in Dimm 1 & 2, and no error LED light upon restart. Then I placed the 2GB's back and swapped around and followed the LED light, and voila, found the culprit RAM. I'm gonna call OWC and see about getting a replacement. Chances are you'll have to do the same.:( You might want to take a look at what OWC memory warranty covers.

    Hope this helps.:)
  5. loblah thread starter macrumors newbie

    Feb 20, 2008
    THANKS for all your replies...

    so... after reading all of this

    i opened up the cover, then rebooted and sure enough there was a red LED light on the upper riser on DIMM 1 of the OLD RAM (the 2 x 1 gb sticks from apple)

    so I reset pram, and still got the red light

    then I switched the top and bottom riser, and still got the red light

    THEN I swapped the 2 sticks of ram on the riser with the red light, then rebooted, and that did it... NO RED LIGHT


    let's see how long this lasts. i hate intermittent problems. i'm a filmmaker with 5 machines of which only one is mac in this edit suite, we got it for final cut pro - and so far this is the only computer i've had hardware problems with... c'mon Apple, prove to me that you deserve to be sitting next to these high-powered windows-based Avids.

    a google search revealed that i'm not the only one with RAM/red LED light issues.

  6. Consultant macrumors G5


    Jun 27, 2007
    It seems to be a problem with third party RAM.

    Apple does not make the third party RAM.

    It's not an Apple problem. Jeez.
  7. UltraNEO* macrumors 601


    Jun 16, 2007
    I've experienced something like this in the pass... I've discovered some modules like to have priority, therefore those need to be placed on the top riser and other's on the lower. (However, if you have four sticks, they should two on each! That's if it's a 2008 MacPro.)

    Sometimes it's just good to shuffle the modules about... I can't explain that...

    All my slot are full... Need more RISERS! :D
  8. Tom Sawyer macrumors 6502a

    Tom Sawyer

    Aug 29, 2007
    Thought I'd chime in as I have experienced the same VERY FINICKY ram setup in a 2008 MP. I actually went on ebay and bought 6 more oem 1gb Apple dimms, pulls from MP's. 8gb is plenty for my needs and it was a cheap way to get there. The dimms arrived and I was pleased to see they were the exact same brand and model as my oem dimms. So I popped them all in and only 4gb showed up with every other slot showing populated in Profiler. Long story short, after much dimm swapping, even though these dimms were all 'exactly' the same brand/model wise the MP still 'required' me to put the original 2 dimms next to eachother on the top riser. There were three trailing numbers on the dimms (firmware/revison?) that did vary and the originals had 030, 4 of my new ones had 042 and two others had 029. Once I put the dimms in as REALLY perfectly matched pairs all 8 gb showed up. Obviously even within the same brand/model number there is still 'matching' pairs. I've upgraded a LOT of machines memory wise and this situation was a first. :eek:
  9. ObaMaciden macrumors member


    Nov 4, 2008
    I'll have to give swapping RAMs around a shot. For now I'm down to 14GB (2x6GB + 2x1GB). Though I haven't yet maxed out 14GB yet, it just bugs me about having to pull out the 2x2GB I paid for. Hopefully OWC makes it easy to exchange if swapping can't fix.:p

    Anyone having particular problems with OWC's 2GB RAM?
  10. sickmacdoc macrumors 68020


    Jun 14, 2008
    New Hampshire
    Actually no biggie but just for clarification that is not the case-- see the Early 2008 Mac Pro Owner's Manual (around page 32 I believe- don't have mine with me right now) or the chart in the DIY Guide on the Apple site at (the third entry- titled "Mac Pro (Early 2008) Memory (FB-DIMM) DIY Replacement Instructions"). If four sticks are used they need to be as two matched sticks in slots 1 & 2 of Riser A (Upper) and two matched sticks in slots 1 & 2 of Riser B (Lower).
  11. sickmacdoc macrumors 68020


    Jun 14, 2008
    New Hampshire
    If it is OWC branded RAM anyway the swap is super easy since it comes with a lifetime advanced replacement policy- by which they will ship replacement RAM before they have gotten your bad sticks. I did that once with some G5 RAM and it was a breeze.:)

    As far as 2Gb OWC modules, I have had no problems with them. I added 6x2Gb to the stock 2x1Gb on my Early 2008 2.8Ghz MP and all 14Gb is working fine.
  12. Dano312 macrumors newbie

    Jan 23, 2009
    Quality control problem with Mac Pros?

    I've had all of these same problems, which started about 6 months after I bought my refurbished MacPro (early 2008). Thankfully still under warranty, so after a trip to the local Apple store, the 2GBs of original Apple memory were replaced as faulty.

    I also had 4gigs from OWC, and soon after returning home, started to get the same sorts of problems. Took the memory out and reseated it, used Stabilant 22 on them (if you don't know about this seems-like-a miracle electronics product--it makes contacts work when you didn't realize you had a problem--check out this kinda quirky Canadian company's site at, and finally got things working again.

    One problem (flashing screen, image coming on and off) seemed to be related to running the LCD at 75Hz. Knocked it down to 60Hz (somebody had posted this same solution) and that solved that.

    But what I noticed and what bothers me is what I take as poorly made memory risers. As I was taking the risers out I looked closely at them, and I have one word for what I see -- crap. It seems like 1/3 of the 'gold' connectors look corroded, enough so that some of the traces are so thin I can see the board underneath. The riser board in general doesn't look anywhere as good (quality of board, colors, coatings, printing) as what I've seen from companies as varied as Asus, HP, Nvidia, the list goes on.

    That just shouldn't be. These are the only way very complex, very high frequency signals move back and forth from the RAM to the rest of the system, and the last time I saw anything as cheap looking as these traces/connectors was probably 20 years ago when I first started to build my own PCs--these were on poor quality video cards from companies no longer in the business.

    I couldn't believe this. I know Apple is famous for making very high margins on its hardware--to the envy of the rest of the industry--but this is no place to do it. Look at the connectors on any video card, on your RAM memory, and then compare these to the connectors on risers: the cards and RAM have a thick, bright coating of metal--and look solid.

    The risers have "made in China" printed on them. I'm sure there is a lot of good technology that comes out of China, but I'd prefer (if it existed) to buy something made in Taiwan (or even better, the good ol USA), where they generally seem to worry about quality control.

    I'm not enough of an engineer to know if this could be causing these memory problems (which I've found posted on lots of other sites)--but come on Apple--don't try to save a few pennies here.
  13. jjahshik32 macrumors 603

    Sep 4, 2006
    Should have bought RAM from, I think their the best 3rd party for Mac Pro RAMs.
  14. KRF68 macrumors newbie

    Mar 13, 2010
    venice, ca
    maybe a dumb question... do you see these LED lights? Do you open the side while the computer is on?

  15. whizpup macrumors newbie

    Mar 4, 2010
    IF your model Identifier is MacPro3,1 then you must follow the rules shown in this doc precisely:
    Earlier MacPro1,1 and MacPro2,1 models not only use different RAM but the order is also different in how the risers are populated. Purchased in 2008 does not mean it is in fact a 3,1. You MUST go by your model ID rather than year or processor speed, etc. and are excellent sources for certified MacPro RAM. Mac RAM Direct also offers the exact Apple OEM Nanya parts for a fraction of Apple's $. Only get fully Certified RAM for these machines.
    To zero in on an issue I suggest populating your risers progressively. Install one pair and boot up.. then another pair and boot.
    As an Apple tech I can tell you the Mac Pro machines have infinitely more RAM issues than any other Mac. Both from low grade RAM and improper installations. Read the installation doc and follow it to a tee... these are NOT PowerMacs and do not follow any of the rules we all know from earlier machines..
    Also, one module will make it's pair appear bad as well in the system...and full insertion and clipped down is another easy error, double check this too.

    Hope this is of some help :)
  16. maghemi macrumors 6502

    Aug 7, 2009
    Melbourne Australia
    So when you swapped the risers, was the red light still on the same riser, or did it stay with the top slot?

    I had this same issue and went through all the tests and checks like you did. After much moving around I got it working by swapping ram modules and the like, but eventually got the problem again.

    The thing I noticed was it was always the same place on the same riser regardless of what ram was where.

    For me it turned out to be a faulty Ram Riser card. Sometimes the Ram slot just wouldn't work. It was replaced and haven't had the same problem again.

    Correct, apple does not make Ram............ Even the stuff they sell in their machines......

    It's not always third party additions that are at fault. And sometimes it is apples equipment that is faulty ........... Jeeez.
  17. lannister80 macrumors 6502


    Apr 7, 2009

    If they're on, they're quite bright and obvious. They're small LEDs surface-mounted on the RAM cards (on the end nearest you).
  18. hellobye macrumors newbie

    Oct 8, 2006
    I JUST had this issue a few weeks ago!

    You just have a bad batch of ram.
    I ordered two 4 gigs sticks. I saw a red light in my memory riser when the ram wasnt recogized. My applications were crashing all the time etc.

    So I just wrote OWC customer support my issue. Ended up talking to a Customer service rep. They gae me a return code. Since their ram comes with lifetime warranty the replacement was free!

    just ask for a replacement. its all good.:eek:

  19. amirshah macrumors newbie

    Apr 1, 2010
  20. ShockDoc macrumors newbie

    Aug 12, 2010
    New Zealand
    I had an issue too installing an additional 4x4GB from RAMCITY. Below is the fix that worked, thanks to the suggestions from this forum.

    I had 2x1GB in the top riser (the original mem) and 2x2GB in the bottom Riser (Buffalo)
    Adding the 4x4GB from RAMCITY into the remaining dimm slots as matched pairs and resetting the PRAM did not
    result in the system recognising and using all the memory. It recognised a mixed bag of old and new ram.

    The Fix was to remove all the RAM.
    Initially load the RAMCITY ram top and bottom Risers in positions DIMM1 and DIMM2
    Reset the PRAM and start up. Recognised 16GB.

    Shut down and then add the 2x2GB (Buffalo) RAM to Top Riser Position DIMM3 and DIMM4
    Reset the PRAM and start up. Recognised 20GB

    Shut down and then add the 2x1GB ("Apple") RAM to Bottom Riser Position DIMM3 and DIMM4
    Reset the PRAM and start up. Recognised 22GB

    All seems to be running OK so far

    Thanks for the suggestions!

    Attached Files:

  21. reel2reel macrumors 6502a


    Jul 24, 2009
    Hmm. We've got seven Mac Pro's (2008's) running here and not one single hardware problem in two years.

    Our six old Avids, on the other hand, are collecting dust in the basement because the HP's kept breaking down and everyone gave up.

    Funny how life is so varied and unpredictable!
  22. PLDD macrumors newbie

    Oct 1, 2010
    A simple thing to check.

    I am a Mac novice and this is my first upgrade.

    I had the same issue. Upgrade a 2GB Mac Pro 3.1 with an extra 4GB of RAM.

    I followed the advice and put the new 2c2GB RAM in the top card and relocated the 1GB of RAM to the bottom. The new 4GB was recognised and I had a red LED on the bottom card.

    I swopped them around to no avail.

    I then noticed that on the bottom of each stick of RAM does not have symmetrical connections. There is a small plastic lug two thirds of the way down the socket, which corresponds to a small cut out on the stick of RAM.

    It is quite simple to fit them in the correct slots but the wrong way around - trust me I achieved this: brute force and ignorance.

    Once I noticed this and aligned the lug/slot in for each stick it worked. The red LED went out and the RAM showed up in the config.

    I guess it is one of those things the old pros know and don't realise newcomers don't see it. I read all the support sites and watched videos of "how to install" before doing this but no one mentions the sticks are asymmetrical and need to be lined up. Most just grab the stick and click it in...!
  23. philipma1957 macrumors 603


    Apr 13, 2010
    Howell, New Jersey
    If you put them in the wrong way and then corrected it and it works consider yourself to be lucky. If it breaks in the next few weeks due to the if it does not fit force it method. here is a link for a new memory holder.

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