Expansions: CF vs. MD vs. SD

Here is a small comparison of Compact Flash (CF) Cards, Multimedia Cards (MMC), and Secure Digital (SD) Cards.  More will be added as new devices and technologies are released.  Note that all devices that support Compact Flash cards, support CF Type I or Type II (unless specified).

  Compact Flash Multimedia Card Secure Digital
Devices Pocket PC Based devices, Handera devices. Casio EM-500 Pocket PC Based devices, Palm devices.
Current Expansions Memory, Modem (POTS and GSM), Networking (Ethernet, 10BaseT, and BNC), Wireless (RF), GPS, Connectivity (Serial and USB), Data Input (Bar Code), Bluetooth, 802.11b Memory Memory, Bluetooth
Future Expansions 802.11a Modem, MP3 Player, Digital Still Camera, GPS, Bluetooth, Barcode scanner Modem, MP3 Player, Digital Still Camera, GPS, Barcode scanner

Card Technical Specs (based off SanDisk Memory Cards)

  CF Type I CF Type II Multimedia Card Secure Digital
Pins 50 7 9
Length 36.4 mm 36.4 mm 32 mm
Width 42.8 mm 24 mm 24 mm
Thickness 3.3 mm 5 mm 1.4 mm 2.1 mm
Weight 11.4 mm 13.5 mm 1.5 g 2 g
Voltage 3V/5V Dynamic 2.7-3.6V 2.7-3.6V
Transfer (Burst) Up to 20Mbytes/sec Up to 2.5Mbytes/sec Up to 2.5Mbytes/sec
Transfer (Sustained) Approx. 1.4 Mbytes/sec    
Sleep to Read 2.0 msec 1.0 msec 1.0 msec
Sleep to Write 2.5 msec 1.0 msec 1.0 msec
Current Sizes Up to 512mb Up to 64mb Up to 128mb
Future Sizes 1gb + 128mb + 256mb +
Cost for 32mb $18 $24 $30
Cost for 64mb $32 $43 $45
Cost for 128mb $53 (Not Available) $78
Cost for 256mb $103 (Not Available) (Not Available)

* Some specs/info on SD cards is limited or not available.  Transfer rate for SD is based on number of data lines.  1 Data Line = 2.5mb/sec, 2 Data Lines = 6mb/sec, 4 Data Lines = 10mb/sec.
** Prices came from pricegrabber.com on April 2002 for SanDisk memory cards.
*** Specs for Transfer rates and power usage are maximum for top models

Feel free to email me about your own PDA, questions, comments, articles, rumors, and reviews.  I can be reached at dave@davespda.com.