Secure Digital Cards
By Chris De Herrera, Copyright 2006
 Version 1.00  Revised 12/10/2006

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There are a few different Secure Digital cards.  This FAQ explains the differences and compatibility between the versions of Secure Digital cards including the MultiMedia Card, MultiMedia Card Plus, MultiMedia Card Mobile, Secure Digital Card, mini SD, micro SD and SD HC.

Prior to the Secure Digital card the MultiMedia card was released.  The MultiMedia card is the exact same size as the Secure Digital card and in most devices it is backward compatible.  The MultiMedia cards were produced up to 128MB of storage.  The big differences are that the MultiMedia card does not have a serial number and do not have a write protect switch.  You can use a MultiMedia card with a card reader so you can easily copy your data to the card from your PC.

MultiMedia Card Plus

This is a higher speed MMC card.  They are the same size as the SD card (.94" x 1.26" x .06") and have similar performance.  However they do not support the serial number function or the write protection.

MultiMedia Card Mobile

The MultiMedia Card Mobile is a smaller MMC card.  With an adapter you can use it in a standard MMC based device.

Secure Digital Card (SD)

The Secure Digital card is 0.94" x 1.25" x 0.08".  It provides up to 2 GB of storage.  Generally 1 GB storage cards can be used universally with all devices however some devices require a rom upgrade to support 2 GB.  You can use a SD card with a card reader so you can easily copy your data to the card from your PC.  For the best performance you will want to look at the highest speed SD card.  They vary from 60x to 133x.  1x refers to the standard speed of a CD.  You cannot use a SD card in a device that supports a MMC card only.

mini SD

The mini SD cards are smaller (.84" x.78" x.05") and they are designed to work in smaller devices such as a cell phone.  They support up to 2 GB of storage and generally 1 GB cards are universally compatible.  With a SD adapter you can use the mini SD card in a SD based device.  You can use a mini SD card with a SD adapter and card reader so you can easily copy your data to the card from your PC.  If you plan on upgrading to a device that supports a mini SD card then consider getting one now and use it with an adapter until you get the new device.

micro SD

The micro SD cards are very small (.43 x .59 x .039) and it is designed to work in smaller device such as a cell phone.   They support up to 2 GB of storage and generally 1 GB cards are universally compatible.  With a SD adapter you can use the micro SD card in a SD based device.  You can use a micro SD card with a SD adapter and card reader so you can easily copy your data to the card from your PC.  If you plan on upgrading to a device that supports a micro SD card then consider getting one now and use it with an adapter until you get the new device.

Secure Digital HC Card (SD HC or SD 2.0)

The SD HC card (0.94" x 1.25" x 0.08") is a new generation of Secure Digital cards that is designed to be higher speed.  Also, SD HC card allows you to store more than 2 GB - theoretically up to 2TB.  At the present time the largest SD HC card is 8GB.  The bad news is that SD HC cards are NOT backward compatible with SD devices even though they will fit in the slot.  So if you want to use larger cards you will have to look for SD HC compatible devices.  The SD HC cards were first released in May, 2006.

Card Readers

I suggest that you get a USB 2.0 card reader or a PC Card adapter.  They both offer higher performance compared to older USB 1.0 card readers especially when you have a lot of content.  As always make sure you eject your media in Windows 2000 or XP before removing it.  If you corrupt the card you can use applications like Norton Utilities to check and fix the card.  Also, not all devices can support FAT32 or NTFS file formats so I suggest that you format the card in the device you want to use it with.

(All images courtesy of Kingston Technology)