27" random shutdown (previous shutdown cause: -128)

Discussion in 'iMac' started by f00f, Jul 8, 2011.

  1. f00f macrumors 65816


    Feb 18, 2009
    New Yawk
    I have a mid-2010 27" i5 iMac (my 3rd iMac in as many years) maxed out with 16GB of Crucial memory. I'm aware that iMacs have potential issues with 16GB configurations -- there's tons of noise about it all over the net.

    Seems a workaround is simply to not run 16GB configurations. I'm a huge abuser of VMware and would rather not knock the mem config down if I can avoid it. According to some posts online, iMacs are very picky about their memory modules and the particular brand of chips used on the modules but my research is thus far inconclusive about what brands work and what don't. So I'm reaching out here to anyone who may have experienced this "random shutdown syndrome" and managed to solve it without sacrificing memory count. What brand memory has been working for you (16GB configuration only) in your late iMac?

    Also, after these random shutdowns occur (and it's totally random; could happen once in a couple months or a few times an hour) the kernel.log advertises the "Previous Shutdown Cause" as -128. Does anyone know what this code means? One post I came across implied that it means the SMC simply doesn't know why the machine shut down (not very useful!)


    PS -- The only common ground I can find between the random shutdowns the machine has had is that I'd been working in Safari just prior to the shutdown. I'd literally click on a link then *poof*, black screen. Reproducible? Unfortunately not. Not at will anyway (which is a characteristic of memory problems).
  2. macdudesir macrumors 6502

    Jan 16, 2011
    Blacksburg, VA
    I've seen many places that say Samsung RAM works but i cannot confirm this as i only have 12GB of crucial RAM :(
  3. kevrayner macrumors newbie

    Feb 19, 2011
    this is what mine is doing...Factory built by apple top of the range with 16gb ram

    I get the random -128 shutdown

    Help !!!!

  4. shortcut3d macrumors 65816

    Aug 24, 2011
    Samsung memory seems to fix the problem. Also, try Lion and the latest EFI updates. I definitely experienced a lot of problems with Crucial. Samsung, OWC, Kingston, then Corsair are my preferred brands in Macs in that order.
  5. Macman45 macrumors G5


    Jul 29, 2011
    Somewhere Back In The Long Ago
    I Run 16GB

    on my iMac. Came with 8 and I bought and installed another 8GB from Crucial. No issues at all. If it's a RAM issue, maybe you could get them swapped out?

    Have you runs memory test on the machine? You could just have faulty chips.

    Another thing to check is that the modules are firmly and correctly seated in the slots. It requires a surprising amount of force to get them to click properly into place,
  6. kevrayner macrumors newbie

    Feb 19, 2011
    All the stuff thats in the mac came from apple and was fitted by them so havent got a clue

    Apparently now its been escalated to a super senior engineer !!!

    They best effing sort it out !

  7. laws215 macrumors newbie

    Dec 19, 2011

    I have this EXACT problem with the same iMac. It's been a problem since the day I've bought it a year ago. It happens at least once a day, totally random shut downs. I've tried many software workarounds to no avail.

    Hopefully the off-brand 16GB ram is the issue. I ordered Samsung to replace my brand. (By the way, vendors like OWC won't credit your purchase because as far as they know, the ram complies with Apple's spec.)

    Keep this thread alive for anyone else having this same problem.
  8. kevrayner macrumors newbie

    Feb 19, 2011
    My Imac 27 inch was specced up by apple...the ram inside 16gb is what they put in...there are no after market items in the Imac.

    I had a call the other day from apple after 12 months of ****** random shutdowns and numerous emails and phone calls to applecare they are sending me one of the new Imac models...I just hope I don't have the same problem ?

  9. shortcut3d macrumors 65816

    Aug 24, 2011
    This problem only appears to affect 2010 27" iMacs configured with 16GB of RAM. Now that 32GB are available at a reasonable price, there appears no issue there. I can only confirm that Samsung 16GB (4 x 4GB) and Corsair (4 x 8GB) do not exhibit this behavior.
  10. kevrayner macrumors newbie

    Feb 19, 2011
  11. laws215 macrumors newbie

    Dec 19, 2011

    From OWC, I installed 16 GB of Samsung RAM (only $120) and swapped out my 16 GB of unknown RAM (I asked using the Mfg code, but they didn't know). Over a week without a crash.

    Not scientific, but to me, this fixed a very annoying problem. If your mid-2010 iMac suffers from random kernel panics, the RAM issue described in this thread is worth a try.

    btw - as previously mentioned, the "bad" RAM is technically Apple-compliant, so no refunds :[

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