PIO stands for Programmed Input/Output, which is a protocol for data transfer. Since it involves the CPU, the use of PIO mode for data transfer can slow a computer down considerably. On the contrary, DMA (Direct Memory Access) does not involve the CPU. Rather, the involved components move data directly to and from RAM, bypassing the CPU altogether. Therefore, DMA has better performance in data transfer than PIO.
Moreover, DMA can be divided in two types, Multi-word DMA and Ultra DMA. The main difference between these two models is that Ultra DMA can serve faster data transfer speeds than Multi-word.
Transcend provides different product models in order to satisfy a variety of requirements from our customers. For example, Transcend’s CF/75/80/120 are designed based on Multi-Word DMA; CF133/266/CF 100I are designed based on Ultra DMA. CF45I is designed on the PIO model.
Note: Not all types of computers support Ultra DMA. If you are not sure whether your system supports UDMA or not, please contact your device retailers or technical support department.