New SD card speed classification system arrives

For high-performance SDHC and SDXC cards

THE SD ASSOCIATION has announced new high-speed symbols for SDHC and SDXC cards which are once again meant to make our lives easier. The old Class 2, 4, 6 and 10 ratings will be kept for older memory cards that don’t meet the new UHS or Ultra High Speed SD [PDF link] card standard. The new UHS speed classification has plenty of room to grow, especially as we’ve only hit the first generation of SDXC cards.

There are two new symbols to go with the UHS standard, the first one is a large, bold, capital I. This symbol means that your SDHC or SDXC card supports data transfer speeds of up to 104MB/s. This standard doesn’t appear to have any performance related figures when it comes to write speeds, only read speeds, which is a bit odd. You’ll also need a device what supports the new UHS-I memory cards to take advantage of the new, faster cards, although they’re fully backwards compatible with SDHC and SDXC devices as long as you’re using the correct memory type for your device.

The other part of the UHS standard is a symbol that looks like a large U with the digit 1 in it. This marking will also be found on SDHC and SDXC cards and it indicates that the card meets the UHS Speed Class 1 performance levels. The SD Association didn’t disclose what the lowest write performance level of this type of card will be, but the cards are meant to be fast enough for real-time video recording directly to the cards. As the best consumer AVCHD camcorders offer a bit rate of 24Mbps, or about 3MB/s, the performance requirements need to at least exceed this.

The only problem right now is that there aren’t all that many devices that support SDXC to start with and there are even fewer devices out that that supports these new standards. You can’t use the UHS cards in current devices either, as the cards aren’t backwards compatible. Then again, considering how much a 64GB SDXC card costs, it’s not really an issue for most consumers, but 32GB SDHC cards are starting to become affordable, although the new faster cards are likely to come at a premium.S|A

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