ATA, DMA?

ATA - (AT Attachment) is the general standard for connecting disk drives. ATA covers a range of data transfer methods:

PIO - (Programmed Input/Output) The CPU reads the data from the disc interface and writes it to memory.

DMA - (Direct Memory Access) is where the circuitry on the disc controller card relieves the CPU of much of its memory read/write activities (Bus Mastering). This frees up the CPU to carry out other non-memory access tasks.

UDMA - (Ultra-DMA) An improved version of DMA, this methos uses techniques of improved timing and data pipelining to double the maximum data transfer rate achieved by standard DMA.

PIO:

Mode, Speed, Standard.

0, 3.3Mbps, ATA
1, 5.2Mbps, ATA
2, 8.3Mbps, ATA
3, 11.1Mbps, ATA-2
4, 16.7Mbps, ATA-3 (standard speed for non-DMA CD devices)
5, 22Mbps, Not implemented.


DMA:

Single Word 0, 1.04Mbps, ATA
Single Word 1, 2.08Mbps, ATA
Single Word 2, 4.17Mbps, ATA
Multiple Word 0, 4.7Mbps, ATA
Multiple Word 1, 13.3Mbps, ATA-2
Multiple Word 2, 16.7Mbps, ATA-3


UDMA:

0, 16Mbps, ATA-4
1, 24Mbps, ATA-4
2 (UDMA/33), 33Mbps, ATA-4 (DMA enabled CD devices & older HDDs)
4 (UDMA/66), 66Mbps, ATA-4 (More recent HDDs)
5 (UDMA/100), 100Mbps, ATA-5 (Commonly used HDDs)
6 (UDMA/133), 133Mbps, ATA-6 (Newest HDDs)

UDMA/xxx is commonly refered to in HDD specs as ATA/xxx

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