HP provides various ways to find and install drivers for your HP 840 G9:
While not technically a "driver," the BIOS (Basic Input/Output System) controls the hardware initialization. HP frequently releases BIOS updates for the 840 G9 to address security vulnerabilities (like the "BIOSphere" vulnerabilities) and improve system stability. These should be applied with caution, ensuring the laptop remains plugged into power during the process. hp 840 g9 drivers