PPT Slide

I/O Techniques

No interrupts

Interrupts

I/O to memory transfer through processor

Programmed I/O

Interrupt-driven I/O

Direct I/O to memory transfer

Direct memory access (DMA)

• DMA unit uses the bus to transfer data to/from memory
  • when the CPU is not using it, or
  • forces CPU to temporarily suspend (cycle stealing)

• I/O channels
  • selector
  • multiplexor

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