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USB 2.0 external drive transfer speeds - confused !!

Discussion in 'PC Hardware' started by Ian, Jul 10, 2004.

  1. Ian

    Ian Guest

    Is there anyone that can help me understand whether my external USB 2.0
    drive is transferring at the correct speed. At first I thought that it
    was only transferring at 1.1 speeds but I think I mixed up Mbit and
    Mbyte speeds.

    Anyway, using SiSoft Sandra reports a transfer speed of:

    11,036 kB/s

    At first I thought this must only be operating at USB 1.1 speed but then
    I notcied that the Sandra program had a reference benchmark of 11,610
    KB/s for a Hi-Speed USB ATA 100 drive. I am using a Maxtor 200Gb ATA
    133 drive so now I am confused as to whether this is operating at USB
    2.0 which I thought was 480 Mbit/s which = 60 MB/s ??

    Help please !
    Ian, Jul 10, 2004
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  2. Ian

    Rod Bartlett Guest

    This is close to 7.5 times faster than the theoretical maximum for USB
    1.1 so your external drive is definitely operating as a USB 2.0 device.
    The 480 Mb/s maximum for USB 2.0 is the speed without overhead. It
    would be impossible for a single device to achieve that full throughput
    rate. To get anywhere close, you'd need a device which was capable of
    streaming data with no intervention. The latency of issuing disk
    commands across USB is going to have a detrimental effect on throughput

    The theoretical maximum for USB 1.1 is 12 Mb/s but in practice, you
    can't get more than around 9 Mb/s. There's just too much overhead in
    the USB protocol.

    - Rod
    Rod Bartlett, Aug 19, 2004
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