Mac Pro 4.1 - 5.1 memory matching problem

Discussion in 'Mac Pro' started by rueyloon, Aug 27, 2014.

  1. rueyloon macrumors regular

    Sep 24, 2013

    hi, I just received 4 X 8GB from my ebay purchase (one of the 4 is dead, but that's another story)

    I currently have
    4 X 4gb and
    4 X 1gb on my Mac Pro giving me 20gb in total

    I can't seem to match the 8GB with any of my existing RAM, they are all 8500 ecc ram. I can't seem to find any info about ram not matching except the 16GB modules (info from OWC).

  2. h9826790 macrumors G4


    Apr 3, 2014
    Hong Kong
    Are they all UDIMM or RDIMM? You can't mix them together.
  3. rueyloon thread starter macrumors regular

    Sep 24, 2013
    Thanks I think you are right, the new RAM is stated at 8500R, my current ones is just plain 8500.
  4. stjames70 macrumors member

    Jul 5, 2009
    Same problem

    I bought certified mac ram from RAMJET to augment the six 8gb 1333MHz sticks I had on my 4,1. The two new sticks I got were placed on slots 4 and 8 -- they caused my Mac not to boot up and the front power white LED to blink quickly.

    Called RAMJET and after verifying installed memory, I found out they sent me the supported unregistered DIMMs and I had registered DIMMs in my machine.

    Ok. So they exchange the two 8 GB sticks with registered DIMMs.

    You know what? Same problem. So I am thinking.....problem with slots 4 and 8?

    So I swapped my existing slots 3 and 7 with the new memory to test the theory. And guess what? Blinking white LED of death on power button again!

    Exchanged to original ram sticks, and voila, normal boot.

    I think I may have to look carefully at the exact Hynix memory that is on that computer and try to obtain the exact same 8gb sticks.

    Geez, I will tell you if that works. But I think that when you are upgrading memory, stick with the same vendor all the way through, whomever it is.
  5. rueyloon thread starter macrumors regular

    Sep 24, 2013
    I manages to pair the 12gb that came from the nMP with the uRam in my oMP.
  6. 666sheep macrumors 68040


    Dec 7, 2009
    That's perfect way, but not a must. Specs must match, that's basically all. Don't mix 2R with 4R, registered with unbuffered etc. Vendor and memory speed does not have to be the same.

Share This Page