USB 3.0 add on help

In brief... could someone please help me understand my bottleneck using USB 3.0 devices? I just bought a Sigg Inc USB 3.0 PCIe add in card with bay hub and when transferring files to a portable HD (also USB 3.0) I'm only getting an avg of 70mb/s data transfer rate. I've updated every driver I can think of and windows appear to recognize the portable HD as 3.0 however when I look through device manger most of my USB hubs are listed as either High Speed or Full Speed including the 3.0 hub. Would moving the add on card from the PCIe x1 slot to my available PCIe 2.0 x16 slot help. (would that drop my graphics card to x8)? I wasn't expecting the 5gb/s obviously but I thought I'd be close to 250 mb/s range...

Windows 7 64bit SP1
Phenom II X4 965 Black 3.4 GHz (NO OC)
16gb (4x4) CORSAIR XMS3 DDR3 1333
Single XFX - ATI Radeon HD 4670
1 500MB Barracuda 7200rpm 3GB/s HD
1 1TB Barracuda 7200rpm 3GB/s HD
Siig Inc USB 3.0 PCIe i/e w/ 4 port bay hub
WD Passport USB 3.0 portable HD 1TB
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  1. Best answer
    70MByte/sec is probably about right for a portable external hard drive, especially if it's accessing the inner cylinders. The spec sheet for the 1TB WD Scorpio Blue drive (which is a fair guess for what's inside your WD Passport enclosure) shows a max sustained transfer rate of 124MByte/sec, which would decrease so something like 60 to 65MByte/sec for the slower innermost tracks.

    You have to understand that hard drive speeds are limited by the density and the spin rate of the platters, not by the SATA or the USB connection. (Well, they ARE limited by a USB 2.0 connection, but not by a USB 3.0 connection).

    So even though you have a 3Gbit/sec Hard drive or a ~500MByte/sec USB 3.0 connection, the drives themselves are not going to get anywhere close to that speed.
  2. Best answer selected by ell0361.
  3. Thank you, makes sense now
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