/ˈʌl-trə diː-ɛm-eɪ/
n. “An advanced version of Direct Memory Access (DMA) for faster data transfer between storage devices and system memory.”
Ultra DMA, also known as UDMA, is a technology that enhances the traditional DMA method used with PATA and early SATA storage devices. It allows for higher-speed data transfers between storage drives and CPU memory by using improved signaling techniques, including faster clock rates and more efficient data encoding.
UDMA supports multiple transfer modes, each offering a higher maximum throughput than the previous generation. For example, UDMA modes range from UDMA 0 (16.7 MB/s) up to UDMA 6 (133 MB/s), making it one of the fastest interfaces for legacy PATA drives.
Key characteristics of UDMA include:
- High-Speed Transfer: Significantly faster than traditional PIO or early DMA modes.
- DMA-Based: Offloads data transfer tasks from the CPU.
- Multiple Modes: Different UDMA modes provide varying maximum transfer rates.
- Improved Signaling: Uses techniques such as cyclic redundancy check (CRC) to ensure data integrity at higher speeds.
- Backward Compatibility: Compatible with older ATA devices supporting standard DMA modes.
Conceptual example of UDMA usage:
// Ultra DMA workflow
Enable UDMA mode in BIOS or controller
Drive and controller negotiate highest supported UDMA mode
DMA controller transfers data directly between drive and memory
CRC ensures data integrity during high-speed transferConceptually, UDMA is like upgrading a delivery highway to a multi-lane express route, allowing data to flow between storage and memory much faster than before, all while letting the CPU focus on other tasks.