iMac with Samsung 850 Evo SSD Problems

Discussion in 'iMac' started by Hand of Ike, May 1, 2015.

  1. Hand of Ike, May 1, 2015
    Last edited: May 1, 2015

    Hand of Ike macrumors newbie

    Apr 27, 2015

    I have been running my Samsung 850 Evo SSD via usb for a couple of weeks now with no issues. I took the plunge and opened up my iMac and installed it internally (I have a 27" Late 2009, Yosemite 10.10.3).

    Two things, 1st I guess is common but I am a little confused about. The HDD fan is now whirling at full speed - I expected this and thought that I could sort this via software, but none of the fan control software works (HDD Fan Control Monitor, SSD Fan Control, SMC Fan Control, Macs Fan Control) none of them do anything to the fan. Am I missing something as others seem to get this to work?

    I am keen on sorting this with a hardware fix, less keen on 'shorting' the sensor cable than I am fitting a sensor like on the ODD - is this possible to do? Or is the only way to sort this to 'short' it? Can anyone point me in the direction of instructions on how to do this?

    Just to note I fitted the SSD via a 2.5 to 3.5 adapter into the space the old HDD drive occupied, the ODD is still fitted internally and I am using the sensor fitted there to regulate the ODD's fan speed; I'd want to fit a similar sensor to the HDD fan that the ODD has.

    2nd, the drive is now being run on the internal SATA cables but it is slower (boots a little slower, opens apps a little slower) than when I had it running from USB 2.0. Again am I missing something that I need to do to get this drive running faster? I thought that running it directly off the SATA cables internally would speed the data transfer up.

    Thanks for taking the time to read this, and my gratitude to anyone who can offer any help.
  2. macthefork, May 1, 2015
    Last edited: May 1, 2015

    macthefork macrumors 6502

    Feb 2, 2013
    A temperature sensor cable can be bought from OWC that will allow the iMac to operate it's fans properly based on the Drive Temperature. It's not recommended to short the sensor, because this will not allow the fan to ramp up if it needs to.

    What size is that SSD? Is it nearly full? With Yosemite you cannot enable TRIM without creating a serious security hole. In my experience, operating a SSD without TRIM does cause it to slow down in the Mac after a few months time depending on usage. But, size will surely be a factor with a smaller, more full drive having more trouble with this than a larger capacity drive with more free space.

    if you're able to boot into an earlier version of the OS such as Mavericks, Mt. Lion, etc. you can run the TRIM command through the "Repair Disk" command in Disk Utility, or just run TRIM Enabler to allow an efficient cleanup of the SSD. Then switch back to Yosemite until you notice a slowdown again.

    The SATA II in that iMac should be substantially faster than USB 2.
  3. Hand of Ike thread starter macrumors newbie

    Apr 27, 2015
    Thanks I will look into that....

    It's a 500GB drive and it isn't even close to being half full. I have enabled TRIM via 'TRIM Enabler', all seems okay (the speed of the drive isn't noticeably different with or without TRIM.

    That is what I thought too, how would I go about investigating what is the problem?

  4. spatlese44 macrumors 6502

    Dec 13, 2007
    Typically from a thumb drive or other USB connected drive, or is there some way to partition the SSD? Either way, no big deal. I was all worried about the TRIM issue, but this doesn't sound too difficult. It's about time I got an SSD. I'll be going for a 500 GB one, which is about twice what I need.
  5. macthefork macrumors 6502

    Feb 2, 2013
  6. Hand of Ike thread starter macrumors newbie

    Apr 27, 2015
    Tested with AJA Test it reports Read Speed of 249.9 MB/s and Write of 207.8 MB/s.... Is this as fast as I can expect? I was hoping for around 500 MB/s.... But it is still slower on the SATA than via USB 2.0 which I think is odd...

    I think I've found an easier hardware option to remedy the fan by fitting a transistor to the cables that acts as a temperature sensor, lots of reports that it works - so I am going to look into this further as it will cost about $1 instead of $39.95+ Shipping (to the UK)
  7. yjchua95 macrumors 604

    Apr 23, 2011
    GVA, KUL, MEL (current), ZQN
    It's normal. USB 2.0 will only give around 60MB/s or even less. SATA2 will give the speeds you posted.

    USB 3.0 will give around 420MB/s or so with UASP, and SATA3 itself will give 510MB/s+.

    I tested it with my Samsung 840 Pro 512GB, mounted in an Archgon ASMT-2105 based enclosure with UASP-USB3.0 and also with my 2011 15" cMBP with SATA3.
  8. Hand of Ike thread starter macrumors newbie

    Apr 27, 2015
    Thanks for that, I'm still puzzled why my system works faster with the Samsung in USB 2.0 than when plugged into the SATA 2.... Could there be something else slowing this down? I did replace my SuperDrive that had stopped working at the same time as fitting the SSD. I fitted a Panasonic UJ-265 Blu Ray Drive, into the ODD space, could this be slowing things down? Both drives work, but if I try to play Blu-Ray movies via 3rd Party Software it's really stuttery on the video track (fine on the audio)... I actually ripped a Blu Ray to the SSD using MakeMKV and that splutter exactly the same, does this point to another issue?

    Thanks for the replies
  9. macthefork macrumors 6502

    Feb 2, 2013
    As mentioned, USB 2 will not give you the speeds you're seeing with the SSD connected to SATA II. When you mention that your speeds are faster on the USB buss, are you talking about the first time an application is opened after a shudown? Or, an application opening after sleep.

    The combined speed of the drive and buss, either USB or SATA will only apply when opening an application the first time after shutdown. This because anything loaded into RAM will be deleted during shutdown.

    After sleep, or reopening the same application later, leaves the application still loaded into RAM, and therefore will load much faster regardless of how the SSD is connected. so, it may appear to load faster, even though the SSD is connected through USB2.

    The real test of SSD speed and buss speed is when you first open an application after a shutdown.

    Those speeds you show are within what they should be for SATA II. If you were to do the same test with that SSD connected to USB 2, You'd see a substantial reduction in speed.
  10. Hand of Ike thread starter macrumors newbie

    Apr 27, 2015

    It is noticeably slower when opening an app or a file for the first time, it's slower on booting too. It's so noticeably slower on the SATA 2 than USB, whatever I am doing. I'm not doubting that the drive will come back with slower reading via USB than these SATA readings which is concerning me that something else is happening with my setup. I won't be able to access my system until tomorrow to put the SSD back into the USB configuration.

    It's baffling me what is going on, and I'm not sure how I'd go about diagnosing it.

  11. macthefork macrumors 6502

    Feb 2, 2013
    You also could try opening Console Log in your Applications > Utilities Folder and watch what occurs when opening an Application. See if there's any process holding it up.
  12. Hand of Ike, May 3, 2015
    Last edited: May 3, 2015

    Hand of Ike thread starter macrumors newbie

    Apr 27, 2015

    I could just reattach the LCD temp sensor that I left unplugged......

    Feel really stupid, went in to mess with the drives this morning and there it was dangling around, reattached and all thinks are working now, even the Blu Ray Drive and the HDD Fan.... Feel really stupid, but happy! My Mac is working at great speed!!

    Even thought the fan is now not spinning out of control I think I might do the transistor temp mod.

    Sorry to have wasted your time, thanks for all the replies everyone!!
  13. macthefork macrumors 6502

    Feb 2, 2013
    Thanks for letting us know the resolution to the problem. Sometimes it is a simple fix that we just didn't consider. It's never a waste of time if we've learned something...
  14. briloronmacrumo macrumors 6502


    Jan 25, 2008
    FWIW: IIRC trimming can be done by booting into single user mode ( command + S on restart ) and then using the
     fsck -fy 
    command followed by
    The bottom of the fsck run should show a message:

    Verify and Repair volume "******"
    Repairing file system.Checking Journaled HFS Plus volume.
    Checking extents overflow file.Checking catalog file.
    Checking multi-linked files.Checking catalog hierarchy.
    Checking extended attributes file.
    Checking volume bitmap.
    Checking volume information.
    Trimming unused blocks.
    The volume ****** appears to be OK.
    File system check exit code is 0.

    Works here on a Samsung 840 EVO as a 2011 iMac boot drive ( OS X 10.10.3 )

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