The Word DMA (WDMA) interface was the fastest method used to transfer data between the computer (through the
Advanced Technology Attachment
Parallel ATA (PATA), originally , also known as IDE, is a standard interface designed for IBM PC-compatible computers. It was first developed by Western Digital and Compaq in 1986 for compatible hard drives and CD or DVD drives. The connection ...
(ATA)
controller
Controller may refer to:
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* Controller or financial controller, or in government accounting comptroller, a senior accounting position
* Controller, someone who performs agent handling in espionage
* Air traffic controller, a person ...
) and an ATA device until
Ultra Direct Memory Access (UDMA) was implemented. Single/Multiword DMA took over from
Programmed input/output
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* ''Programmed'' (Innerzone Orchestra album), 1999
* ''Programmed'' (Lethal album), 1990
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* P ...
(PIO) as the choice of interface between ATA devices and the computer.
The WDMA interface is grouped into different modes.
In single transfer mode, only one word (16-bit) will be transferred between the device and the computer before returning control to the CPU, and later it will repeat this cycle, allowing the CPU to process data while data is transferred. In multiword transfer mode (block mode), once a transfer has begun it will continue until all words are transferred.
Two additional Advanced Timing modes have been defined in the
CompactFlash
CompactFlash (CF) is a flash memory mass storage device used mainly in portable electronic devices. The format was specified and the devices were first manufactured by SanDisk in 1994.
CompactFlash became one of the most successful of the e ...
specification 2.1. Those are Multiword DMA mode 3 and Multiword DMA mode 4. They are specific to CompactFlash. Multiword DMA is only permitted for CompactFlash devices configured in True IDE mode.
{, class="wikitable"
, +DMA Modes
!Mode
Max Transfer Rate ( MB/s) | Bits | Min cycle time | Defining standard |
, Single 0
2.1 | 16 | 960 ns | ATA-1 |
, Single 1
4.2 | 16 | 480 ns | ATA-1 |
, Single 2
8.3 | 16 | 240 ns | ATA-1 |
, Multi 0
4.2 | 16 | 480 ns | ATA-1 |
, Multi 1
13.3 | 16 | 150 ns | ATA-2 |
, Multi 2
16.7 | 16 | 120 ns | ATA-2 |
, Multi 3
20 | 16 | 100 ns | CompactFlash 2.1 |
, Multi 4
25 | 16 | 80 ns | CompactFlash 2.1 |
AT Attachment the category