for the Lexar Professional 800x 16 GB compact flash card what does the UDMA7 mean ?
UDMA 7, which stands for Ultra Direct Mode Access 7, is the latest transfer mode under the UDMA interface. UDMA 7 allows a maximum transfer rate of up to 167MB/sec.
The device (eg, a camera) must be UDMA 7 capable to take advantage of the increased speed capability; otherwise, the card will operate at the device's slower speed. However, the device is only half of the picture. A fast card reader can take advantage of the card's speed when transferring data to a computer.