The CompactFlash Association website has some brief information on the UDMA support in new CF cards.
“DMA interface mode is included and reduces the processor power required to manage the CompactFlash data transfers. True IDE Ultra DMA 133 interface mode increases the CompactFlash interface maximum data transfer rate to 133MB/sec. This UDMA interface mode is well defined and tested by the usage on IDE hard disk drives. Faster PC-Card ATA UDMA memory modes are also included and can provide maximum interface data transfer rates up to 133MB/sec. With the UDMA feature, forward and backward compatibility is maintained with systems and CF cards even operating with the interface data transfer rate of 16MB/sec.”
They also mention that CF cards are safe from airport X-ray machines.
UDMA CF normally supports programmed IO transfer (PIO) modes (which max out at 150x) and UDMA, which is 300x.
(The Lexar “x” speed rating describes minimum write speed capability where x=150KB/sec sustained write speed.)
Nikon has UDMA CF support in their latest camera bodies, the D300 and D3, while Canon doesn’t. Generally, Canon lags one generation of CF support from Nikon.
Regardless of which cameras you own, UDMA will speed up new card readers for copying files to your computer.
I use Sandisk and Lexar Pro CF cards. My Nikon D200 is noticeably faster at writing images to a CF card than Canon 30D because Nikon support PIO5 mode, and has a very large image buffer. (The D200′s large image buffer mean that CF speed is not that important to overall performance and any CF card is fine in practise.)
Lexar labels their new pro UDMA CF cards as “UDMA 300x.” They cost only a few dollars more than PIO-only cards.
Likely I will standardize on Lexar 8G UDMA this fall. I’ve had good experiences using Lexar cards and they always seem to be in stock at Fry’s Campbell.
Lexar Professional UDMA 300x CompactFlash
B&H: Lexar 8 GB UDMA CF
dpreview.com: Lexar 300x CompactFlash cards and new readers
Fake SanDisk Compact Flash card
