Differences Between an SD and MMC Memory Card

SD and MMC Memory cards look pretty much identical to one another, however, these cards are actually different for a number of different reasons. There are several things that set these cards apart from one another. It's important to compare these to ensure that you choose the right card for your computer.

Write Protect Switch

SD Cards have a built in write protect switch; this switch can be used to prevent the images on the card from being erased or overwritten. The write protect switch is a small piece of plastic which doesn't actually do anything. It works in a similar way as the read write switch on an old 3.5" diskette.

Improved Design

The contacts of the memory card are slightly recessed under the plastic, which prevents them from coming into contact with fingers and anything else.

Increased Capacities

The original MMC standard allowed for a maximum of 1GB, however, newer versions of the technology have increased this up to a maximum of 32GB. SD is available in 3 variants: SD Memory Cards, SDHC and SDXC. SDHC have a capacity limit of 32GB. SDXC are the newest types of cards and these have a theoretical limit of 2TBs.


SD cards are an extension of MMC memory cards; this means that it's possible to use MMC cards in newer SD devices. It's also possible to use regular SD cards in SDHC and SDXC devices.

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