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Helpful ReplyUSB 3.0 and 3.1 total bandwidth?

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ZoranC
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2020/08/23 12:18:00 (permalink)
xDevs page for X299 Dark says USB 3.0/3.1 has 5/10Gbps per port which would make one think total bandwidth of USB 3.1 ports is 20Gbps and of USB 3.0 is 40Gbps (for 8 total USB3 ports, 6 external + 2 internal).
 
However, same page later says “rear panel features eight USB3 ports, with two of them having 10 Gbps bandwidth (red Type-A port and Type-C port) and rest six at 5 Gbps” and manual for X299 Dark goes on to say USB 3.0 ports support up to 5Gbps and 3.1 up to 10Gbps implying bandwidth is shared on some level.
 
So how is bandwidth shared / what is total bandwidth / how many “lanes” are used for USB3 and 3.1?
 
Is it really per port for a total of 20Gbps for 3.1 and 40 for 3.0?
 
Or it is per -root hub- for a total of 10Gbps for 3.1 and 20 for 3.0?
 
Or -both- 3.1 ports share 10Gbps and -all 8- 3.0 share 5Gbps?
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    EVGATech_GabrielT
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    Re: USB 3.0 and 3.1 total bandwidth? 2020/08/24 08:32:38 (permalink) ☄ Helpfulby ZoranC 2020/08/24 11:04:49
    Hello,
     
    This has been discussed in the link below for how USB 3.0/3.1 function. This will be able to explain it better than I could. 
     
    https://electronics.stackexchange.com/questions/291566/usb-3-0-bandwidth-per-individual-port
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    ZoranC
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    Re: USB 3.0 and 3.1 total bandwidth? 2020/08/24 11:12:57 (permalink)
    EVGATech_GabrielT
    Hello,
     
    This has been discussed in the link below for how USB 3.0/3.1 function. This will be able to explain it better than I could. 
     
    https://electronics.stackexchange.com/questions/291566/usb-3-0-bandwidth-per-individual-port




    Thank you Gabriel! Do I interpret that correctly as saying all USB 3 ports are connected through / sharing single PCIe lane and all USB 3.1 ports two lanes, hence the total bandwidth is bandwidth of single/two lanes which is 5/10 Gbps?
     
    Also, what about USB 2.0 ports (internal headers) on your mb? Do they have their own lane and thus do not share bandwidth with USB 3.0 ones or they share same lane?
    post edited by ZoranC - 2020/08/24 11:32:27
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    Monstieur
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    Re: USB 3.0 and 3.1 total bandwidth? 2020/09/25 16:31:41 (permalink)
    The Intel USB 2.0 / 3.0 ports and headers have independent bandwidth as they come straight from the X299 chipset, bottlenecked by the ~32 Gb/s DMI link. These don't use PCIe lanes as there is no controller in-between - the PCH directly exposes a single USB root hub on the PCI bus. Multiple ports should not slow each other down unless the DMI bandwidth is exceeded. It's possible there is some USB bandwidth sharing inside the chipset, but only Intel really knows.
     
    The 2x ASMedia ports are 10 Gb/s each, bottlenecked by the ~16 Gb/s ASM2142 PCIe 3.0 x2 controller, further bottlenecked by the ~32 Gb/s DMI link.
    post edited by Monstieur - 2020/09/25 17:40:15
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