USB module bandwidth issue with optical devices (4177, 4077, 7505, 7505M, 7024, 7024М, 7028, 4197, 7701M, 7708)

Ilya Tahil -

Current CPUs with modern energy-saving features can cause bandwidth limitations on USB. This is a direct consequence of CPU cores falling into so-called sleep states. CPU cores enter these sleep states independently from the load level on the USB. This can lead to the following malfunctions:

- Low USB bandwidth provided by the PC system

- TransferFailed errors occurring even at moderate pixel clock settings

- Camera operates at low speed only

- Black images receiving

To fight the low USB bandwidth provided by the PC system:

  • Please remove other USB devices from the system (USB keyboard and mouse are fine). Run tests with only one device connected at once.
  • Make sure to use a USB port directly on the mainboard. Front panel or other ports are connected to the mainboard with poor cabling quality frequently.
  • Make sure to use USB2.0 certified cables to connect the device.
  • If you are using USB hubs or extensions: Run a test without these devices, connect the device directly to the PC.
  • Disable other equipment that is connected via USB. For example, WLAN and Bluetooth adapters might use a USB to connect.
  • If you are using a mobile PC: run it on main power, not the battery.
  • Check your energy-saving options in the operating system. Disable energy-saving features and set the available features to “full performance” or similarly named options.
  • If you checked the above and still observe low USB performance you might be experiencing the issue with CPU sleep states (Windows 10).

To fight the 'sleep' states:

  • Download CPUDISABLE C2 C3.reg file by following this link
  • Run CPUDISABLE C2 C3.reg (by running this file the C3 condition will be disabled in the Windows registry)
  • Reboot your PC


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