USB 3.0 speeds on late 2012 iMac

Discussion in 'iMac' started by lcavada, Mar 10, 2013.

  1. lcavada macrumors newbie

    Sep 30, 2011
    I have been knocking my head in trying to hook up an external drive enclosure through USB 3.0 ports in back of late 2012 iMac 27 inch.

    I have tried 3 different enclosures, and the results are about the same. Only getting about 40MB/s (320mb/s). Everwhere i read that USB 3.0 will run at 5GB/s.

    I went into detail with the support department of one of the enclosure manufacturers. We tried everything possible, and his conclusion was the Apple did not design the USB 3.0 ports to standradds, thus the enclosure cannot achieve such speeds. For that matter any other USB 3.0 device will not reach those speeds.

    With 3 different enclosures I got the same speeds.

    I also bought a USB 3.0 hub. I am not sure the hub is running at USB 3.0 speeds. How can i check?

    NOTE, i did not connect the drive enclosures to the Hub.

    So what do i need to do to make sure my iMac runs its USB ports at USB 3.0 speeds.

    iMac (27-inch, Late 2012), OS X Mountain Lion (10.8.2)
  2. COrocket macrumors 6502

    Dec 9, 2012
    USB 3.0 is 5 Gb/s, not 5 GB/s. Are you reading a hard drive? Unless you are reading a really fast SSD, you are maxing out the read/write performance of the disk, not necessarily the connection speed. This could be a possible explanation why you are getting the same speed with 3 different enclosures.

    IMO, the company you contacted tried to blame Apple so you would not get upset with them.
  3. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    Open System Profiler and have a look at the USB Section there, if you have a USB 3 Device connected you can see the speed it is working at.

    Oh, and what COrocket said.
  4. lcavada thread starter macrumors newbie

    Sep 30, 2011
    OK, noted the 5 Gb/s. I am reading a hard drive. 7200 RPM drive. WD1001FALS. Drive came with my 2011 iMac, i removed it since i upgraded.

    Should it still not be faster than the speeds I am getting?



    I temporarily took off my USB 3.0 drive enclosure.

    I still have the USB 3.0 hub connected.

    According to system profiler, is it running at :

    Product ID: 0x0024
    Vendor ID: 0x8087 (Intel Corporation)
    Version: 0.00
    Speed: Up to 480 Mb/sec
    Location ID: 0x1a100000 / 2
    Current Available (mA): 500
    Current Required (mA): 0

    Shouldn't it be running faster?

  5. Raima macrumors 6502

    Jan 21, 2010
    The bottle neck is the hard drive. It can only transfer so much.

    Like the others have said, unless you are transferring SSD to SSD via USB3, you won't really be pushing the potential of what USB3 is capable of.
  6. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    If the hub is connected it runs at USB (480Mb/s) as you can see.
    You need to attach the USB 3 drive to see if it runs full speed or not.
  7. lcavada thread starter macrumors newbie

    Sep 30, 2011
    OK, so if i go and buy an external thunderbolt drive from Apple, does this mean i will not get the advertised speed of 10 Gb/s ?

    The hard drive will slow things down? How much slower, what speeds shall i see ?


    But this is a USB 3.0 hub. Should run up to 5Gb/s. Why is it not running at this speed?

    What speed/throughput should i see for the USB 3.0 connected hard disk ?

  8. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    No, the weakest link is the HD, if you have an SSD it will make a difference, HD's are slow.


    As others have said, the HD is the slow one, you will not see high speeds with it.
  9. lcavada thread starter macrumors newbie

    Sep 30, 2011
    So if i get speed of 40MB/s (320mb/s), this is the correct speed?
  10. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    Bit low, but it's running at USB 2 speeds and I think that's more or less it, I have a Firewire 800 and it maxes out at around 70 MB/s, FW is 800 Mb/s.
    It has an HD inside.
  11. lcavada thread starter macrumors newbie

    Sep 30, 2011
    here is the spec on the hard disk i am using

    Western Digital
    1.0TB Caviar® Black™ / Apple ROM Hard Disk Drive
    3.5-Inch | SATA 3.0Gb/s | 7200RPM | 32MB Cache

    Why can't i get this throughput of 3.0Gb/s using the USB 3.0 connection which is rated at 5Gb/s?


    those speeds i can see. I had a FW800 external drive and those are the speeds i got.

    How come using USB 3.0 i cannot get faster than this speed?
  12. Raima macrumors 6502

    Jan 21, 2010
    Ok, let me put it this way. You have a high grade freeway that is capable of vehicles travelling over 300mph. This high grade freeway is your USB3 or Thunderbolt.

    How fast you actually travel on the freeway depends on the vehicle that you use.

    In this analogy, a hard disc drive (HDD) is simular to a bicycle, while a Solid State Drive (SSD) is simular to a Bugati Veyron (a very fast sports car).

    If you want to transfer data fast, you must have a fast drive like a SSD, as well as a fast connection method like a USB3 or Thunderbolt.

    Does this help with your understanding?
  13. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    Connect the drive directly to the Mac, then look in system Profiler and see if it's running at USB 3 or USB 2 speeds, click on the USB entry where the external is attache, normally it would give two instances of USB 3 speeds, but if it runs at USB 2 speeds it will tell you.

    Otherwise just post a screenshot.(Hit Command-4, then hit spaceBar for window capture)

    Edit: How much was the External enclosure, cheap ones have cheap controllers and it has been mentioned to be a problem sometimes.
  14. COrocket macrumors 6502

    Dec 9, 2012
    With today's hard drive technology, you will not see 10Gb/s, unless you are RAID-0ing a bunch of disks. Thunderbolt and USB 3.0 are capable of higher speeds than most components today, so that the interface has the ability to run future devices as they get quicker.

    It sounds like your hub is running at USB 2.0 speeds. Try plugging your 3.0 enclosure directly into your mac and see what speeds you get then.
  15. Serban Suspended

    Jan 8, 2013
    those specs for USB 3.0 or thunderbolts port are the maximum you get regarding the device you are using it. That maximum specs are only available for SSD.
  16. kennyap macrumors regular

    Jul 14, 2012
    Cayman Islands
    I have a My Passport 1TB USB 3.0 drive connected, see below for my System Report. I get 70MB/sec speed transferring to my Drobo 5D Thunderbolt DAS. I know that in my case the actual 1TB drive is the bottleneck.

    My Passport 0748:

    Product ID: 0x0748
    Vendor ID: 0x1058 (Western Digital Technologies, Inc.)
    Version: 10.15
    Serial Number: 575833314138324B31393032
    Speed: Up to 5 Gb/sec
    Manufacturer: Western Digital


    I would agree that the enclosure is the bottleneck. Are the enclosures you are using all USB 3.0 certified?
  17. Ppq macrumors newbie

    Jul 23, 2012
    my 2TB WD GreenPower via i-Tec usb3 enclosure puts 115MB/s through on PC w. intel chipset.
  18. lcavada thread starter macrumors newbie

    Sep 30, 2011
    OK, thanks so much for all the replies. I am getting a much better understanding of the situation.

    As I contact the enclosure manufacturers they tell me their enclosure is certified USB 3.0. However that Apple is not certified per the standards on USB 3.0.

    So its clear that i will abandon the efforts with the drive enclosures. Cant keep working on something that will end in frustrations.

    A truly certified enclosure will probably cost more than an actual drive!

    I have attached to my iMac a certified USB 3.0 drive by by Western Digital. I have attached the system profiler information. See attached.

    It does show that the drive is connected to a port that can be as fast as 5Gb/s.

    So far so good.

    Then i do a drive speed test using Blackmagic Design Speed test app.

    Reported drive speeds are 75.6 MB/s for read and write.

    I then do another test by copying a file from iMac internal fusion drive to the external USB 3.0 drive.

    File is 4,396,618,989 bytes, and copies to USB 3.0 drive in 59 seconds.

    4,396,618,989 bytes / 59 seconds = 74518965 bytes per second

    This matches the Blackmagic app speed so i have to assume this is the drive speed in USB 3.0

    Will i suffer the same type of disappointment in getting a thunderbolt drive?

    Since its a hard disk inside, will the speed also be around 75 MB/s ?


    Attached Files:

  19. lcavada thread starter macrumors newbie

    Sep 30, 2011
    Looking around, did not see a price for this case. It appears to be a single drive case.

  20. justperry macrumors G3


    Aug 10, 2007
    In the core of a black hole.
    This has been explained to you many times yet you ask again, the HD is the weak link and you will NOT see any improvements with Thunderbolt, you have a HD inside, if you want higher speed buy an SSD!
  21. mushroomtip macrumors 6502


    Oct 27, 2012
    I think what everyone is telling you , your port can handle 5Gb/s , but your Hard Drive In your external cannot.
  22. Fishrrman macrumors Pentium


    Feb 20, 2009
    So long as you use a "platter-based" hard disk drive in your external enclosure, your speeds are going to be somewhat limited because an HDD is slower than the speeds the connection is capable of.

    Put an SSD in that same enclosure, and get back to us....
  23. szw-mapple fan macrumors 65816

    szw-mapple fan

    Jul 28, 2012

    I bought a USB 3 SSD and the speed was roughly 3 times my HD. Go figure.:p
  24. vladfein macrumors regular

    May 28, 2012
    75MB/s is above USB 2 limit, so the connection is certainly USB 3.
    According to Tom's Hardware (,2017-3.html), you should see an average speed of 85MB/s and the max at 106MB/s from your drive.
    There is no faster operation than copying a single large file, so I would expect the speed close to 100MB/s.
    You copy from Fusion drive, but we don't know if the file is on the SSD part of it. Could you copy it in the opposite direction? Than we can count on it to be placed in the SSD's 4GB "catch-all" part, so you would really measure your HDD read spead and USB transfer.
  25. thedeske macrumors 6502a

    Feb 17, 2013
    Late 2012 and 2013 Macs are capable of 200 per second on HD with the right USB3 single external enclosure via a new UAS protocal. Lacie, Caldigit, and a few others have this in some of their products. I personally witnessed 200 up and down on a recent install with an iMac & Caldigit AV Pro external. The same device loaded with SSD reaches over 400.

    UAS first arrived on a few PC boards mid 2012
    Not a peep from Apple on this, but it's there.

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