8a420f71_BSOD_Index__Parameter_4
[Parameter 1] 0x3 (Windows XP and later) [Parameter 2] The physical device object (PDO) of the stack [Parameter 3] The functional device object (FDO) of the stack [Cause] A device object has been blocking an IRP for too long a time. [Parameter 4] 
The blocked IRP
BSOD Index
Parameter 4