Hardware interrupts-from I/O devices, processor, memory Software interrupts-produced by a program.
Direct Memory Access (DMA)
Interrupt or Polling driven I/O incurs considerable overhead
Transfer high amounts of data at high speed without continuous intervention by the processor
DMA controller keeps track of memory locations, directly transfers to memory (using the bus)
independent of the processor
Special control circuit needed in the I/O device interface which is called a DMA controller