ISR vs DPCs #WindowsInternals #ProcessorDebug (1/5)
ISR: A software routine that hardware invokes in response to an interrupt. ISRs examine an HARDWARE interrupt and determine how to handle it. (2/5)
DPC: Software interrupt with a lower priority than the ISR
An ISR must perform very fast to avoid slowing down the operation of the device and the operation of all lower priority ISRs. (3/5)
An ISR must perform very fast to avoid slowing down the operation of the device and the operation of all lower priority ISRs. (3/5)
To provide timely service for hardware interrupts, Windows – with the cooperation of device drivers – attempts to keep the IRQL below device IRQL levels. (4/5)
One way that this goal is achieved is for device driver ISRs to perform the minimal work necessary to acknowledge their device, save volatile interrupt state, and defer data transfer or other less time-critical interrupt processing activity for execution in a DPC IRQL. (5/5)
Capturing high DPC and ISR: 
Microsoft recommend that a single (1 count) DPCs or ISRs should not run longer that:
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