From: joemonk64@gmail.com   
      
   > I don't know if plugging in a USB device causes an interrupt,   
   > but if it does, the BIOS/UEFI gets control and does its stuff,   
   > and then informs the OS via an agreed interrupt that the OS   
   > hooked in to that there is a new device available?   
      
   The OS comes first in the interrupt chain, not the hardware. The OS will trap   
   the interrupt, especially in PM.   
      
   See https://docs.microsoft.com/en-us/windows/win32/devio/wm-devicechange   
      
   Joe   
      
   --- SoupGate-Win32 v1.05   
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