Slow USB Speeds

Discussion in 'MacBook Pro' started by MKang25, Sep 25, 2011.

  1. MKang25 macrumors regular

    Jun 12, 2010
    The MBP I have in my signature is having problems with both its USB ports. I noticed a few days ago when I connected my USB flash drive that the transfer speeds were slow. So I tried switching to the other USB port and still found slow speeds, so I tried a different USB flash drive and still found very slow speeds, transferring a 1GB file to the flash drive was taking 3 minutes. Other things like connecting my iPod and syncing it took forever. When I check system profiler and USB, my flash drive and everything else shows that its connected as USB 2.0 and showing that max speeds should be 480 MB/s, so I am not sure what is wrong.
  2. Prodo123 macrumors 68020


    Nov 18, 2010
    You did your calculations wrong. USB 2.0 is 480Mbps, not 480MB/s. Which means it's really 60MB/s theoretical max. You're transferring data at around 45.5MB/s, so it's perfectly fine (actually quite good).
    This is why I use FW800 instead of the disturbingly slow USB 2.0.
  3. tunerX Suspended


    Nov 5, 2009
    480Mbps is theoretical and it is in bits per second. Files are measured in bytes.

    Theoretical max of USB 2.0 is 60MBps in bytes.

    In either reference it is still theoretical. The read speed of the internal device, write speed of the external device, and all parts in between those two devices have their own latencies and delays which reduce from the theoretical max.
  4. MKang25 thread starter macrumors regular

    Jun 12, 2010
    Ok, I just got a SSD and I guess suddenly seeing slow transfer speeds threw me off and for some reason I thought they were supposed to be higher then they were.
  5. gorskiegangsta macrumors 65816


    Mar 13, 2011
    Brooklyn, NY
    As others have mentioned the USB 2.0 speeds are up to 480 Mbps (megabits per second), not MB/s (megabytes per second). Since there are 8 bits in one byte, to convert from MegaBits to MegaBytes, divide by 8 (i.e. 480 mega bits per sec/8 bits per byte = 60 megabytes per sec).
    Having an SSD makes no difference if you connect it through USB 2.0 interface - the USB 2.0 interface is bottlenecking any potential speed-up SSDs may offer.
  6. alust2013 macrumors 601


    Feb 6, 2010
    On the fence
    Yeah, those numbers actually look pretty good for USB 2.0. Also, flash drives are notoriously slow, just due to the cheap memory used.
  7. macrumors newbie

    Jul 5, 2008
    Near Edmonton, Alberta, Canada
    notoriously slow??

    I have 2 iMacs, 2006 17" and new 27". I also have an Android OS tablet, 2 year old Win 7 laptop, 1 month old Win 7 All-In-One and 2005'ish Win either on network or to/from flashdriveVista tower. My new iMac, according to the specs, should blow everything else I have out of the water but, when it comes to file transfers, it is the slowest BY FAR than anything I have.. including the Tablet.

    Let's put the math ot 2.0 vs 3.0 megabits and forget the 3.0, essentially, is a clocked 2.0. Why is it that my Win 7 laptop can do in less than 1 minute what it take for my new "humdinger" of a Mac take 12-16 to do??

    I mostly transfer video files back and forth (m4v, mp4, avi & mkv).

    Anyone!? Why is it notoriously slow? From where I stand, because the files are not being scanned by a behind-the-scenes security software, it really should be faster.

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