From LQWiki
PIO stands for Programmed Input-Output. It is nowdays a slow and inefficient data transfer mode. The data is transferred by the processor, byte by byte. This requires processor time and therefore causes a high and unwanted processor load. These issues are somewhat solved with DMA
In Linux, hard drive PIO modes may be tweaked with hdparm. For instance, to set hda to PIO mode 4 (if supported) type
# hdparm -X12 /dev/hda
| Mode | Mbyte/sec | hdparm option |
|---|---|---|
| PIO Mode 0 | 3.3 | -X08 |
| PIO Mode 1 | 5.2 | -X09 |
| PIO Mode 2 | 8.3 | -X10 |
| PIO Mode 3 | 11.1 | -X11 |
| PIO Mode 4 | 16.6 | -X12 |
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