/piː-aɪ-oʊ/
n. “A method for transferring data between the CPU and a storage device using programmed instructions rather than direct memory access.”
PIO, short for Programmed Input/Output, is a data transfer method where the CPU directly controls the reading and writing of data to and from a storage device, such as a HDD or SSD. In PIO mode, the CPU executes instructions to move each byte or word of data, which can consume significant processing resources compared to more advanced methods like Direct Memory Access (DMA).
Key characteristics of PIO include:
- CPU-Driven: The CPU is responsible for all data transfers.
- Simple Implementation: Requires minimal hardware support.
- Lower Performance: Slower than DMA because the CPU handles every data transfer.
- Legacy Usage: Primarily used in older PATA devices and interfaces.
Conceptual example of PIO usage:
// PIO data transfer workflow
CPU executes instruction to read byte from HDD
CPU stores byte into system memory
CPU repeats for each byte or word
Data transfer completes when all bytes are movedConceptually, PIO is like manually carrying each piece of data from the storage device to memory yourself, rather than letting a dedicated mechanism (like DMA) move multiple pieces automatically, which is why it consumes more CPU resources and is slower.