SMS...somebody please settle this

Discussion in 'MacBook Pro' started by AppleGoat, Sep 13, 2011.

  1. AppleGoat, Sep 13, 2011
    Last edited: Sep 13, 2011

    AppleGoat macrumors 6502a

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    #1
    Will the Sudden Motion Sensor kick in for the HD if it's in the Optical Drive? I've heard from some that it doesn't and it is advised to put the HD in its natural bay. However, on the other hand, some have said the SMS is built into the motherboard and is a system wide thing; thus, enabled for an HD where ever it is. I tend to believe the latter, because from my experience I have not heard the clicking sound while the SSD has been in the HD bay. Proving that it is not some mechanism that latches onto the drive once it is moved. Am I right? Please clear this up for me, I have done my homework. Thanks!
     
  2. snaky69 macrumors 603

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    #2
    If there is one built into the hard drive which is in the opti-bay(not all of them have one), yes.

    If not, no. The macbook pro has it's own sensor but it only works for the HD bay.

    Better?
     
  3. AppleGoat thread starter macrumors 6502a

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    #3
    Well, I don't figure my stock Hitachi 5400rpm -- which nearly every MacBook Pro possesses -- has that built-in function. As I said before, there seems to be a lot of contradicting information on the internet:

    When you disable the sudden motion sensor, it does so system wide. The SMS circuitry is on the motherboard itself and therefore it doesn't matter which drive you get (or how many drives you have). If you are nervous about running without that safety net, just leave it enabled. I have been contemplating turning it back on to see what happens (if anything) to the speed.

    Source: http://forum.notebookreview.com/apple-mac-os-x/479350-ssd-optibay-install-mid-2010-15-unibody.html
     
  4. iThinkergoiMac macrumors 68030

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    #4
    This shows a fundamental lack of how SMS works. Which is fine, I'm not trying to criticize!

    SMS (whether inside the drive or on the logic board) works by retracting the read/write head to the parked position whenever the laptop experiences sudden motion or free fall. This makes it so the head cannot come into contact with the platter (where all the data are stored). When it's internal to the HDD, the whole process is handled by the HDD itself.

    It can't be "system-wide" unless the logic board is programmed to look for a HDD in every possible place, which it isn't. It's only programmed to look in the HDD bay. It IS built into the logic board, but it still only applies to the HDD bay.

    Also, that clicking noise you're referring to: it isn't the HDD rattling around inside the computer, it's the read/write head inside the HDD clicking and not being able to move properly, spelling death for the HDD. Just because you can't hear that clicking doesn't mean that the on-board SMS is working, it just means your HDD isn't broken.

    Solution: make sure your HDD has its own SMS and leave it in the optical bay.

    Yeah, that's referring to the SMS on the logic board. It seems that person is unaware that HDDs can also self-contain a SMS and that the SMS has no effect on speed unless you are trying to use your computer while in free-fall (apart from malfunctions on the part of the SMS).
     
  5. AppleGoat thread starter macrumors 6502a

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    #5
    Thanks, is there anyway of telling if my HD has an internal SMS? Mind you, it's the stock Hitachi drive Apple put in my computer and not a third-party drive.

    So you believe that clicking sound is a portent of death?!?! I've heard to the contrary and it only occurs when I pick up my computer.

    I'm bent on leaving the SSD in the HD bay and putting the HD in the Optibay, b/c the SSD is my primary drive. For some reason or another, I'm anal about the primary drive residing in a spot Apple never intended for a drive to reside.
     
  6. snaky69 macrumors 603

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    #6
    Determine the model and check on the manufacturer's website, that's the logical thing to do, no?
     
  7. iThinkergoiMac macrumors 68030

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    Well, if you hear a click when you pick up the HDD, that's most likely the SMS. If you are hearing a clicking sound when the HDD is being used, that's the bad thing. You can find YouTube videos with the sound to figure out what I'm referring to.

    This video looks like a good explanation: http://www.youtube.com/watch?v=vbq8vfs1wYY

    As well you should. Your MBP may have wake from sleep issues if your primary drive is not in the HDD bay. Also, the HDD bay is faster than the optical bay in most MBPs, so if you're using an SSD it would be pointless to put it in the optical bay.
     
  8. DWBurke811 macrumors 6502a

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    #8
    I thought the only issues happened when the battery died and the MacBook tried to copy the RAM to the HDD, as it only looks in the "normal" bay for the boot drive. I wasn't aware of any other issues? I'm planning on putting a 1TB HDD in the main bay, and my Vertex 3 in a OWC DataDoubler.

    And aren't most(all?) of the '11s now shipping with SATA3 on both bays? An my 7,1 has SATA2 on both bays, so no difference there either.
     
  9. AppleGoat thread starter macrumors 6502a

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    #9
    Yeah, my Optical Bay is SATA II and I'm using a SATA II drive (Samsung 470). My HD Bay is SATA III. Although I have nothing to base this on, I have this nagging concern that the drive will somehow run slower in the optical drive, even though it can theoretically reach its SATA II potential in either bay. Today I've been consumed with regret for not getting the 256gb version of the 470, even though its pretty pricey.
     
  10. DWBurke811 macrumors 6502a

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    #10
    It will run EXACTLY the same in either bay, your SSD thinks both bays are SATA2; the 470 doesn't know SATA3 exists, and therefore won't see ANY benefits from being plugged into SATA3.
     
  11. AppleGoat thread starter macrumors 6502a

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    There's nothing else that could possibly slow it down? The system isn't tailored to delivering a faster connection to the HD bay?
     
  12. DWBurke811 macrumors 6502a

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  13. AppleGoat thread starter macrumors 6502a

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    #13
    While that is true, I'm still a bit uneasy about putting my primary drive in the optical bay. After all, the system is configured to read the primary drive from the HD Bay. Although I don't often deplete my battery, the hibernation issue may be a harbinger of many small annoyances with displacing your primary drive. I read somewhere that the computer doesn't boot quite as fast from the optical drive, any merit to this person's claims? Still, wondering what I should do. Equally uneasy about about putting an HD in a SMS-less location. Then again, my Powerbook G4 HD probably didn't have that and ran well for 6 years before I sold it. Additionally, over that span of time, I used merely 40 of the 60GB that came on my hard drive, if I could convince myself I could live off twice off as many gigs then the idea of installing another drive is really defeated.
     
  14. gullySn0wCat macrumors 6502

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  15. DWBurke811 macrumors 6502a

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    #15
    Agreed.
     
  16. AppleGoat thread starter macrumors 6502a

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    #16
    Well my original question of whether or not the optical drive had SMS was answered. The latest posts were just me unconsciously searching for someone to justify the less practical approach of placing the HDD in the SMS-less compartment.
     

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