What is PIO?

Programmed Input / Output

     Short for Programmed Input/Output, a method of transferring data between two devices that uses the computer's main processor as part of the data path. ATA uses PIO and defines the speed of the data transfer in terms of the PIO mode implemented, as shown below: PIO Mode Data Transfer Rate (MBps) Standard
     A method of data transfer between two devices that uses the system's main processor as part of the data path. On x86 systems, the REP INS and REP OUT instructions implement this data transfer method. INS reads and I/O port and writes the data into memory. OUTS reads data from memory and writes the data to an I/O port. Each time an INS or OUTS instruction is executed, the memory address is updated. The REP prefix causes the instructions to be repeated until a counter reaches zero.
     ATA uses PIO and defines the speed of the data transfer in terms of the PIO mode implemented, as shown in the information below:

PIO Mode	Access Cycle	Transfer Rate	Standard
0	600ns	3.3 MBps	ATA
1	383ns	5.2 MBps	ATA
2	240ns	8.3 MBps	ATA
3	180ns	11.1 MBps	ATA-2
4	120ns	16.6 MBps	ATA-2

ATA-3, ATA/33 and ATA/66 do not have a PIO mode assignment as of yet, although ATA-3 is often used in PIO4 since it is really a correction to ATA-2.

More on this subject
Beginner's Help
BUG Club Home