/ul'tr* D M A/ (Or "Ultra DMA", "UDMA", "Ultra-ATA", "Ultra-DMA/33") A development of the advanced technology attachment specifications which gives nearly twice the maximum transfer speed of the ata-3 standard (pio Mode 4).

ATA-4 Extensions Ultra DMA/33 Synchronous DMA Mode maximum burst transfer rates:

        Mode         Cycle Time         Transfer Rate
                ns                MB/s
        0         235                 16
        1         160                 24
        2         120                 33

This is achieved by improving timing windows in the protocol on the ATA interface; reducing propagation delays by pipelining data transfers and transferring data in synchronous (strobed) mode.

Developed by quantum corporation, ATA-4 has been freely licensed to manufacturers and is supported by intel corporation.