Hard Disk Drive Data Transfer Protocols
Programmed Input/Output (PIO) is a method of transferring data between the running software and a peripheral by means of special CPU instructions. The PIO protocol requires a great deal of CPU overhead to transfer the data. As a result of this inefficiency, a system's performance can be significantly decreased.
DMA (Direct Memory Access) is a hardware-based feature that allows certain devices to access system memory for reading and/or writing independently of the central processing unit (Multiword DMA and Ultra DMA protocols). This feature also allows CPU to perform other work during the reading and/or writing. 80-pin interface cable is required for Ultra DMA-3 mode and higher.
The maximal throughput of data transfer protocols (MBytes/s)
|Multiword DMA-0||4.2||Ultra DMA-6||133|