Interrupts and CPU Types


All CPU types provide some sort of interrupt
It usually is an electrical signal reaching the CPU
Sometimes (e.g. 8086) there is one wire and one protocol
More often there are multiplexing registers
You have a single interrupt entry point
Then a status register tells which one is active
Possibly a second level register details more
Nowadays we have MSI too: Message Signalled Interrupts
They exist in PCI, to simpliy hardware routing
They are the preferrerd IRQ form in PCI Express

Most simple firmware code bases use no interrupt at all
They rely on cooperative multitasking
Or they are just a "while(1)" loop calling some action