Message Signaled Interrupts (MSI)

Message Signaled Interrupts, in PCI 2.2 and later and PCI Express, is an alternate form of interrupt from the traditional pin-signalled system; instead of asserting a given IRQ pin, a message is written to a segment of system memory. Each device can have from 1 to 32 unique memory locations in which to write MSI events to. An advantage of the MSI system is that data can be pushed along with the MSI event, allowing for greater functionality