为什么USB 3.0外置硬盘不能以USB 3.0速度运行？

我最近购买了PCI Express x1 USB 3.0控制器卡（包含NEC USB 3.0控制器），目的是在Linux机器上使用USB 3.0外部硬盘驱动器。我将卡安装在主板上的空PCIe插槽中，将卡连接至电源线，在新端口之一和我的外部HDD之间绞接了USB 3.0电缆，然后将HDD连接至墙上的电源插座。启动系统后，该驱动器将按预期的100％正常工作，但吞吐量除外：它似乎没有使用SuperSpeed 4.8 Gbps连接，而是回落到了高速480 Mbps USB 2.0样式的吞吐量。Disk Utility将其显示为480 Mbps设备，并且运行了几次Disk Utility和dd基准测试，确认该驱动器的SSD容量远远超过40 MB / s（USB 2.0的近似限制），但该驱动器的性能远不止于此。那。

当我连接USB 3.0硬盘时，dmesg显示如下：

[ 3923.280018] usb 3-2: new high speed USB device using ehci_hcd and address 6

我希望在哪里找到这个：

[ 3923.280018] usb 3-2: new SuperSpeed USB device using xhci_hcd and address 6

我的系统当时在2.6.35-25通用内核上运行。然后，我偶然发现了一个论坛论坛话题，该人发现2.6.37-rc5之前的内核中存在一个错误，可能是此类问题的罪魁祸首。因此，我安装了2.6.37通用主线Ubuntu内核，以确定问题是否会消失。没有，所以我尝试了2.6.38-rc3-generic，甚至从2010.02.01起每晚尝试2.6.38，都无济于事。

简而言之，我试图确定为什么在内核中支持USB 3.0的情况下，我的USB 3.0驱动器无法以完整的SuperSpeed吞吐量运行。

有关其他详细信息，请参见此问题下的评论。

与该问题可能相关的输出（从2.6.38-rc3引导时）：

来自的相关行dmesg：

[   19.589491] xhci_hcd 0000:03:00.0: PCI INT A -> GSI 17 (level, low) -> IRQ 17
[   19.589512] xhci_hcd 0000:03:00.0: setting latency timer to 64
[   19.589516] xhci_hcd 0000:03:00.0: xHCI Host Controller
[   19.589623] xhci_hcd 0000:03:00.0: new USB bus registered, assigned bus number 12
[   19.650492] xhci_hcd 0000:03:00.0: irq 17, io mem 0xf8100000
[   19.650556] xhci_hcd 0000:03:00.0: irq 47 for MSI/MSI-X
[   19.650560] xhci_hcd 0000:03:00.0: irq 48 for MSI/MSI-X
[   19.650563] xhci_hcd 0000:03:00.0: irq 49 for MSI/MSI-X
[   19.653946] xHCI xhci_add_endpoint called for root hub
[   19.653948] xHCI xhci_check_bandwidth called for root hub

的相关部分sudo lspci -v：

03:00.0 USB Controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 03) (prog-if 30)
    Flags: bus master, fast devsel, latency 0, IRQ 17
    Memory at f8100000 (64-bit, non-prefetchable) [size=8K]
    Capabilities: [50] Power Management version 3
    Capabilities: [70] MSI: Enable- Count=1/8 Maskable- 64bit+
    Capabilities: [90] MSI-X: Enable+ Count=8 Masked-
    Capabilities: [a0] Express Endpoint, MSI 00
    Capabilities: [100] Advanced Error Reporting
    Capabilities: [140] Device Serial Number ff-ff-ff-ff-ff-ff-ff-ff
    Capabilities: [150] #18
    Kernel driver in use: xhci_hcd
    Kernel modules: xhci-hcd

的相关部分sudo lsusb -v：

Bus 012 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               3.00
  bDeviceClass            9 Hub
  bDeviceSubClass         0 Unused
  bDeviceProtocol         3 
  bMaxPacketSize0         9
  idVendor           0x1d6b Linux Foundation
  idProduct          0x0003 3.0 root hub
  bcdDevice            2.06
  iManufacturer           3 Linux 2.6.38-020638rc3-generic xhci_hcd
  iProduct                2 xHCI Host Controller
  iSerial                 1 0000:03:00.0
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           25
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          0 
    bmAttributes         0xe0
      Self Powered
      Remote Wakeup
    MaxPower                0mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           1
      bInterfaceClass         9 Hub
      bInterfaceSubClass      0 Unused
      bInterfaceProtocol      0 Full speed (or root) hub
      iInterface              0 
      Endpoint Descriptor:
        bLength                 7
        bDescriptorType         5
        bEndpointAddress     0x81  EP 1 IN
        bmAttributes            3
          Transfer Type            Interrupt
          Synch Type               None
          Usage Type               Data
        wMaxPacketSize     0x0004  1x 4 bytes
        bInterval              12
Hub Descriptor:
  bLength               9
  bDescriptorType      41
  nNbrPorts             4
  wHubCharacteristic 0x0009
    Per-port power switching
    Per-port overcurrent protection
    TT think time 8 FS bits
  bPwrOn2PwrGood       10 * 2 milli seconds
  bHubContrCurrent      0 milli Ampere
  DeviceRemovable    0x00
  PortPwrCtrlMask    0xff
 Hub Port Status:
   Port 1: 0000.0100 power
   Port 2: 0000.0100 power
   Port 3: 0000.0100 power
   Port 4: 0000.0100 power
Device Status:     0x0003
  Self Powered
  Remote Wakeup Enabled

完整，非详细lsusb：

Bus 012 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 011 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 010 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 009 Device 003: ID 04d9:0702 Holtek Semiconductor, Inc. 
Bus 009 Device 002: ID 046d:c068 Logitech, Inc. G500 Laser Mouse
Bus 009 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 006: ID 174c:5106 ASMedia Technology Inc. 
Bus 003 Device 004: ID 0bda:0151 Realtek Semiconductor Corp. Mass Storage Device (Multicard Reader)
Bus 003 Device 002: ID 058f:6366 Alcor Micro Corp. Multi Flash Reader
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 006: ID 1687:0163 Kingmax Digital Inc. 
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 002: ID 046d:081b Logitech, Inc. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

全输出：

• 完整的dmesg
• 全lspci
• 完整的

您确定磁盘已插入正确的（USB 3.0）端口吗？看起来您的USB 3.0控制器正在提供USB总线12，但是磁盘已连接到USB总线3。

根据您的dmesg，USB总线＃3由PCI设备'06：01.2：USB控制器：VIA Technologies，Inc. USB 2.0（rev 65）'提供，它将仅为USB 2.0。