Windows 11 may turn off the PS/2 port to save power, failing to wake it up correctly.
Many modern laptops route internal keyboards and trackpads through an internal I2C or PS/2 multiplexer bus. If you update your laptop's pointing device drivers (such as Synaptics or ELAN), it can corrupt the shared kbdclass.sys or i8042prt.sys upper filter configurations in your registry. If your built-in keyboard stops working after a trackpad update, roll back the pointing device driver to restore the keyboard functionality. Missing Hardware Ports on Modern Motherboards
If your device manager shows a yellow exclamation mark next to the Standard PS/2 Keyboard, or if it displays a error, the issue is usually related to disabled registry entry values or modern power management features. Fix 1: Enable the i8042prt Service in the Registry
Unlike USB peripherals, . If you plug a PS/2 keyboard into a running Windows 11 machine, it will not work. You must shut down the PC, plug in the keyboard, and then boot the system.
Ensure the PS/2 port is clean and seated correctly. If you are using a PS/2-to-USB converter, it may be active, and a passive one might be needed (or vice-versa). 6. Alternative: Use a USB Converter
The PS/2 port is disabled in the BIOS/UEFI or the motherboard does not have a functional PS/2 controller.
The primary driver file associated with the Standard PS/2 Keyboard is often referred to as i8042prt.sys , though the device manager usually lists it under the "Standard PS/2 Keyboard" name using the kbdhid.sys (HID Keyboard Filter) and kbdclass.sys files.
: Right-click the Standard PS/2 Keyboard under the "Keyboards" category and select Update driver > Search automatically for drivers .
: Press Win + R , type regedit , and hit Enter.
Windows 11 will detect the port and reinstall the native driver. Method 3: Turn Off Fast Startup
Examine the circular purple plug on your keyboard. Ensure none of the 6 pins are bent or missing.
Standard driver files become corrupted or replaced by generic USB drivers.
Windows 11 uses "Fast Startup" to speed up boot times by putting the kernel into a deep hibernation state instead of shutting down completely. This process often skips checking the PS/2 port altogether. Press the Win key, type , and press Enter . Click on Hardware and Sound , then select Power Options .
If your keyboard started malfunctioning after a Windows Update (e.g., keys repeating, not responding, or typing wrong characters), roll back the driver.
Right-click , select Modify , and change the value data to 1 . Click OK and restart your computer to apply the changes. 2. Reinstall the Driver via Device Manager