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USB 2.0 vs. USB 3.0

  1. Mar 22, 2018 #1
    In flash memories or external HDDs there is a distinction as usb 2 or usb 3. USB 3.0 is faster than USB 2.0 in such devices. But what about the situation for SDD drives? Does this distinction apply to them, too?

    Thank you.
     
  2. jcsd
  3. Mar 22, 2018 #2

    phinds

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    USB is a transfer mechanism. Any device that is capable of send/receive at USB3 speeds will be faster with USB3 than with USB2. It's irrelevant what KIND of device it is; it only matters what its transfer rates are. A device that can only send/receive at USB2 speeds will be no faster with USB3 than with USB2.
     
  4. Mar 22, 2018 #3

    jtbell

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    Do you mean SSD (solid state drives)?
     
  5. Mar 23, 2018 #4
    Yes, a mistake. I thought they were solid state disk drive, but not.

    Thank you.
     
  6. Apr 11, 2018 #5
    The SSD is capable of bandwidth way higher than both USB 2 and 3. You will be limited by your connection, not the drive. I would highly recommend properly connecting it via a SATA connector.
     
  7. Apr 15, 2018 #6
    But isn't there a relation between bandwitdth and connection types, i.e USB types?

    Thank you.
     
  8. Apr 15, 2018 #7

    phinds

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    Absolutely not. That's like saying that the size of your water tank depends on how big your faucet opening is. The SSD has a much higher bandwidth than the USB2 or even USB3 connections and if you have a faster connection, it will handle it. Conversely, if you have a very slow external drive, hooking it up to a USB3 won't make it any faster.
     
  9. Apr 15, 2018 #8

    rcgldr

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    Or better still, connect a SSD to the PCIe bus. Seagate makes PCIe SSD's with up to 8GB/s transfer rates.
     
  10. Apr 15, 2018 #9
    Then can we say that the bandwidth somebody can use is the lower one between the device and the connection type for the device and the PC? If the SSDs have a higher bandwidth than the all connection types, are SSDs using connections at a speed of connection's full speed?
     
  11. Apr 15, 2018 #10

    phinds

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    yes
    Not sure I understand the question, but if I do then yes, ANY device will attempt to communicate at the highest speed possible, but that may not be a continuous function, depending on the device and the connection. Some devices (I don't think SSD's are among them) are set to communicate at discrete bandwidths. (at least that used to be the case. I'm not really up on modern communications technology)
     
  12. Apr 15, 2018 #11
    When transfering data via usb, windows can shows the speeds. In my cases, the speeds are not constant, they are frequently changing between a maximum value and a minumum value. Why is this the case? What is "discrete bandwidths"? Isn't a discrete bandwidth you used above is device's own bandwidth?

    Thank you.
     
  13. Apr 15, 2018 #12

    phinds

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    Because the computer (and possibly the computer on the device) will be doing other things in addition to the transfer.
    No, it is the communication device's bandwidth. Some devices (old dial-up modems come to mind) would transfer at a fixed rate, but if that didn't work it would drop down to a lower rate. There would generally be a handshake between devices to agree on a rate.
     
  14. Apr 15, 2018 #13
    But there are two relevant devices, one is the storage which is pluged into the PC via a connection type and the other is connection type i.e the port and slots. Aren't we already discussing them and their bandwidths? So communication device's bandwidth is confusing to me. Would you please explain it?

    Thank you.
     
  15. Apr 15, 2018 #14

    phinds

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    This thread started off discussing USB transfer mechanisms. That is a communication device. You have STORAGE <-> USB <-> COMPUTER. The USB is the communication device.

    https://en.wikipedia.org/wiki/USB_communications_device_class
     
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