Comparison between an RS-MMC Memory Card and SD
An RS MMC memory card looks very similar to a SD card, but what are the differences? Learning about the differences should make it much easier to ensure that you are choosing the right card, which will be suitable for your camera or phone.
All SD cards feature a write protect security switch. This switch is not included on any MMC cards. When the switch is switched into position it will prevent anything from being erased or written to the card.
Solid State Storage
Both SD and MMC cards are solid state storage. Neither of these have any moving parts which will ensure that they last for as long as possible.
Both the MMC and SD memory cards are the same physical size. These are about the size of a postage stamp which makes them very easy to carry around with you.
The technical design of MMC cards limits their size to 512MB. However, SD cards have much bigger sizes available. Standard SD cards are available in sizes up to 2GB. SDHC or SD High Capacity is available in sizes up to 32GB.
Any device supporting SD cards can also be used with MMC cards without any additional changes. However, devices which support MMC will not support SD cards. Some devices might have a firmware update available to address this.