MultiMediaCard vs. Secure Digital

The past several years has seen an increasing number of portable storage standards, with devices such as digital cameras, MP3 players, PDAs, and cell phones using portable storage to hold their data. Currently, leaders of the pack in portable storage media are CompactFlash and SmartMedia. But not for very long. Experts believe that, because of their smaller form factors and high densities, two others, MultiMediaCard (MMC) and Secure Digital (SD), will become the dominant portable storage media in the near future.

The increasing market for devices that use this type of storage has spawned essentially three schools of thought: Those who support MMC; those who support SD; and those who don’t know which one to support, so they try to leverage both. What’s the difference? Physically, MMC and SD look virtually identical. They are both flash- based storage approximately the size of a postage stamp. SD is slightly thicker than MMC and the SD only has a maximum 64MB capacity, whereas MMC comes in higher storage capacities ranging from 8 to 256MB. By the end of this year we will start seeing capacity for both cards approaching 512MB.

Architecturally, SD cards were created to be able to secure stored data. SD cards cost more than MMCs because of their data protection features. This gives the cards the ability to be used in enterprise applications that necessitate secure transactions. MMCs currently store data in an unprotected format, but recently the MMCA certified an improved MMC standard called SecureMMC with similar capabilities to SD.

The biggest advantage of the MMC standard is that it was developed for all the leading open systems platforms. This includes Linux and all other Unix variants. Linux companies will easily be able to develop products for MMC cards. The SD standard was developed essentially for the Microsoft Windows platform. But to get at the real difference between the two, one must view the forces driving their adoption. As Linux users know, the best technology does not always come out on top.

The MMC standard grew out of a joint development between SanDisk Corporation and Siemens AG/Infineon Technologies AG. The technology is an open standard available to any company who wants to improve upon it or develop products for it. The MultiMediaCard Association (MMCA) was formed to govern this standard. The SD standard was developed by Toshiba, Matushita (Panasonic), and SanDisk. Unlike MMC, SD is a proprietary technology. Any company that wants to manufacture or sell SD cards must pay a licensing fee to these three companies. Rather than technology, the SD Card Association (SDA) focuses more on marketing. Because of considerable industry support, SD is the better known technology. Palm advertises that their PDAs use SD cards when they actually support both cards. “

IT practitioners might be hearing resonance of a quite familiar battle: The increasing competition between MMC and SD calls to mind another David vs. Goliath or Linux vs. Windows. “Toshiba, Matsushita, and SanDisk can spend for one trade show what amounts to my entire marketing budget for this year,” states Andy Prophet, executive director of the MMCA. 

But not everyone is doing battle. A number of consumer product companies manufacture their products to support both card formats. The MMCA has about 100 members while the SDA has about 300. Many companies are actually members of both organizations. A prime example is SanDisk, which not only belongs to both associations but also contributed to developing both standards.