Editing Interrupt (section)

===Doorbell===
{{Unreferenced section|date=December 2020}}
In a [[push button]] analogy applied to [[computer systems]], the term ''doorbell'' or ''doorbell interrupt'' is often used to describe a mechanism whereby a [[software]] system can signal or notify a [[computer hardware]] device that there is some work to be done.  Typically, the software system will place data in some well-known and mutually agreed upon memory locations, and "ring the doorbell" by writing to a different memory location.  This different memory location is often called the doorbell region, and there may even be multiple doorbells serving different purposes in this region. It is this act of writing to the doorbell region of memory that "rings the bell" and notifies the hardware device that the data are ready and waiting.  The hardware device would now know that the data are valid and can be acted upon.  It would typically write the data to a  [[hard disk drive]], or send them over a [[Computer network|network]], or [[encrypt]] them, etc.

The term ''doorbell interrupt'' is usually a [[misnomer]].  It is similar to an interrupt, because it causes some work to be done by the device; however, the doorbell region is sometimes implemented as a [[Polling (computer science)|polled]] region, sometimes the doorbell region writes through to physical device [[Hardware register|registers]], and sometimes the doorbell region is hardwired directly to physical device registers. When either writing through or directly to physical device registers, this may cause a real interrupt to occur at the device's central processor unit ([[CPU]]), if it has one.

Doorbell interrupts can be compared to [[Message Signaled Interrupts]], as they have some similarities.