Current CPUs with modern energy-saving features can cause bandwidth limitations on USB, which is a direct cause of CPU cores falling into so-called sleep states. CPU cores enter these sleep states independently from the load level on the USB. As a result, the following malfunctions can occur:
- 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 after processing the document
To fight the low USB bandwidth provided by the PC system:
- Please, remove other USB devices from the system (USB keyboard and mouse are acceptable). Run tests with only one device connected at once.
- Make sure to use a USB port directly on the mainboard. The 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 and 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 “High performance” or similarly named options. Click on "Change plan settings" for the “High performance” plan. "Change advanced power settings" link from this screen. In the "Power Options" dialog box, you will see different power settings. Expand "USB settings" by clicking the plus sign. Change the settings from Enabled to "Disabled" for both sections "On battery" and "Plugged in".
- 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)
- Go to Control Panel - Hardware and Sound
- Then go to Power Options
- Choose what the power buttons do (on PCs) OR Choose what closing the lid does (on laptops)
- Click Change settings that are currently unavailable to be able to chose the needed option
- Disable the Turn on fast startup (recommended) setting
- Reboot your PC or laptop