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Will a pci slot bottleneck a usb 3.0 card??

Will a pci slot bottleneck a Usb 3.0 card?
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  1. Alright, I'm aware that it does but to what extent? Is it wort buying one?
  2. no.
  3. Here is the speeds for each:

    USB 3.0 was released in November 2008. The standard specifies a maximum transmission speed of up to 5 Gbit/s (640 MB/s), which is over 10 times faster than USB 2.0 (480 Mbit/s, or 60 MB/s), although this speed is typically only achieved using powerful professional grade or developmental equipment.

    These specifications represent the most common version of PCI used in normal PCs.

    33.33 MHz clock with synchronous transfers
    Peak transfer rate of 133 MB/s (133 megabytes per second) for 32-bit bus width (33.33 MHz × 32 bits ÷ 8 bits/byte = 133 MB/s)
  4. Please link the PCI card that has USB3.0, I am looking for one even knowing the limitations.
  5. Anyway thanks for reply, guess ill have to use my pc's only pcie x1 slot. You know what limitations are for the onboard usb header? Or does it depend on the age/make of the motherboard?
  6. What do you have that you think will exceed 133MB/s?

    Anyways attainable USB3 speed is dependant on the chip being used, Toms has an article you should read before selecting a card.,review-32302.html
  7. hmm yes thanks for the reply.
  8. so does my motherboard have to recent enough to have usb 3.0 support? Or will a controller just solve that problem, by the way, 133mb/s is pretty much quad of usb 2.0 35mb/s and it would make faster transfers when i buy a usb 3.0 external, or i might just upgrade the ones i have now.
  9. Best answer
    The controller can be any place. Integrated into the chipset, an add-on chip built into the motherbd (try to find out whats its connected to, usually a pcie x1 link), or an addon card like you're looking into.

    Ok lets say you put a WD Raptor drive in an external usb3 enclosure and lets say it can transfer data at 150mb/s just for the sake of the example.

    if you plug it into the usb2 ports you would see something in the mid 30's to 70mb/s depending on the usb2 controller your plugged in to (some can do 2x speed)

    if you plug it into a usb3 pci controller you will see about 128mb/s (133 minus headroom) but anything else on the pci bus needing bandwidth would subtract from that figure. The PCI bus 133mb/s is total bandwidth, not per device.

    if you plugged it into a usb3 port on a pcie controller then you would see full speed of the controller up to near the 150mb/s of the harddrives ability. You can only exceed the transfer speed of the drive on small files where it would really be transferring from the drives cache and not the platters.

    now exchange that raptor for an SSD at 250mb/s (sata2 speed) and plugged into the pcie USB3 controller and you would see nearly al lof it (250 minus some headroom about 225 I think)

    for most external drive, it doesnt matter where the usb3 controller is as platter based HDD's have a difficult time exceeding even PCI bandwidth.
  10. Alright thanks alot for help.
  11. Best answer selected by conquer7.
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