Super Cards: SDIO

Not long after the SD card first appeared in 2000, developers of the technology realized there was more potential in the format than simple storage. So, they went back to the labs, added I/O (input/output) capabilities, and SDIO (Secure Digital Input/Output) was born. SDIO lets mobile accessory manufacturers create devices you can plug into the built-in SD slots on your PDA, smartphone, and laptop to add extra capabilities to those devices. There was a flurry of initial activity when SDIO was introduced but not much response from consumers. Today only a few vendors make SDIO cards; most common are SDIO cards that add Wi-Fi or Bluetooth, a modem, or GPS (global positioning system) capability. Also available are SDIO cameras, TV tuners, fingerprint readers, and bar code scanners.

MMC: Still At The Table

SD cards are getting all the glory these days, but MMC, the original small form-factor flash storage card, hasn’t gone bust yet. MMCs can use the same slot as SD cards, giving MMCs a large potential user base. Some experts believe MMC just may have a few aces up its sleeve, as well.

Victor Tsai, co-chairman of the MMCA Marketing Committee, sees a few wild cards at play in the memory card game. “Since day one there has always been a placeholder for I/O in the MMC spec,” he tells us, “but there has never been a market push for it. Within the last year, there has been the formation of an MMCIO subcommittee to study [that need].”

The creation of the I/O subcommittee arose from work done in formulating the recently completed SecureMMC spec. Tsai says there is a SecureMMC smart card nearing market release, and other developers are considering products in the SecureMMC format.

What’s more interesting is that the latest MMC standard, 4.1, includes an “innovation spec” for implementing hard drive functions in mobile devices using MMC technology. This so-called ATA on MMC specification lets manufacturers use the existing MMC bus architecture to build tiny hard drives into cell phones and other devices. Models from Nokia and Samsung are already available. Could your next phone be your computer, too?

SDHC
More Storage, Higher Speeds
The New Generation Of SD

Although the SD card’s small size makes it perfect for use in mobile devices, it has presented challenges for card manufacturers in terms of increased storage capacities. However, by 2008 you can expect to purchase standard-sized SD cards with storage space reaching 32GB. This is possible because manufacturers are currently reworking the file system on the cards.

Previously, SD cards used the FAT16 file system. James Taylor, marketing chairman of the SD Card Association, says, “Because of a limitation in the FAT16 file system, there was no way we could do 4GB on flash memory.”

Last year, the SD developers reworked the card’s architecture to use the FAT32 file system. “We went to FAT32,” says Taylor, “and that allowed us to move to a higher density.” Higher density means more storage sectors, and more storage sectors means higher capacity. The new FAT32 cards are branded as SDHC (SD High Capacity).

Guaranteed Speed

SDHC Cards have more than gigabytes going for them. These cards have increased data transfer speeds at rates of as much as 25MBps. But that’s actually not the exciting part.

“We made the bus faster and we introduced what we call Speed Classes,” says Taylor. Speed Classes relate to minimum transfer speeds, a spec consumers don’t often consider, yet it is potentially crucial when out in the field. Suppose you have a once-in-a-lifetime photo op. You have your high-end camera in Fine mode and set to a very fast shutter speed because you want to take a lot of pictures quickly and at a high resolution.

“If you don’t have a guaranteed minimum speed,” he says, “there’s no guarantee that you can actually take those pictures. The shutter might not release because it’s waiting for the data [from the previous picture] to be processed.

“A lot of people care about the fastest possible speed,” Taylor continues, “but actually minimum speed matters more to the user.” SD’s new Speed Classes guarantee that the card doesn’t fall below a certain performance level.

SDHC Cards have three Speed Classes: 2, 4, and 6. Speed Class 2 is good for standard data storage, small image files, MPEG-1 and MP3 files. Speed Class 4 is for higher density image files. Speed Class 6 is a broadcast-level spec that can accept video streams without skips. (On a related note, Panasonic recently announced it is developing SD cards that accept HD video images for use in video cameras.)

The Incredible Shrinking Card

It’s always easier to make things bigger than it is to make them smaller, and standard-size SD cards will always hold more than their smaller counterparts (miniSDs and microSDs), but it’s these two mighty mites that should dominate the flash memory world within the next four or five years. According to Celeste Crystal, analyst at market research firm IDC, “Multiple handsets all around the world are adopting SD slots.” By 2007, her research indicates “miniSD and microSD will become the primary form factors, largely driven by mobile phones.”

Given that miniSD Cards hold about 80% of what a full-sized SD card holds, and microSD about half, these tiny SD cards will soon be able to hold multiple movies at broadcast-quality resolution for watching on your PDA or mobile phone.

View the graphics that accompany this article. (NOTE: These pages are PDF (Portable Document Format) files. You will need Adobe Acrobat to view these pages. Download Adobe Acrobat Reader)