วันเสาร์ที่ 10 ธันวาคม พ.ศ. 2554

SDHC Memory Cards Vs SD Memory Cards

So what are the differences between SD Cards and SDHC Cards?

Ever since the introduction of SD cards a couple of year ago the format has gone from strength to strength. Of course requirements have moved on in terms of video recording technology and photography and SD cards need to move with the times. The introduction of high definition video and high mega pixel photography would not have been possible if the SD organization had not come up with a faster storage system than the limited 2gb SD card standard.

Memory Card

So they have introduced the SDHC memory card standard. SDHC stands for "Secure Digital High-Capacity" and is now available and is based on the Secure Digital Association or "SDA" 2.00 specification. SDHC memory card standard provides removable SD card memory storage of far great capacity of up to 64gb for all types of digital devices. This includes digital cameras, MP3 players, camcorders, PDAs, and much more.

The new SDHC cards guarantee the user a minimum sustained data transfer speed which is a change from the SD card way of doing things which supplies a maximum speed guarantee. The SDHC card comes in three speeds - Class 2, Class 4 and Class 6.

The new SD card, SDA specifications allows for all manufacturers to share common sustained data transfer speed standards. This was something that was not possible with the old SDA standards. The idea behind the new speed classification approach is that it allows the user to select the card speed based on the needs of individual applications, such as High Quality Photography and HD video, rather than basing their assessment on just a maximum SD card speed rating.

Although the SDHC memory cards use the same SD card physical format, they cannot be used with any SD card host device that does not comply to the new SDA Specification, Version 2.00.

This is not the same in the reverse. Any host device that complies to the SDA Version 2.00 standard can use both SD Card and the new SDHC Cards.

Another variation between the two cards including the formatting system used. All current SD memory cards on Version 1.01 and Version 1.10 use either the file system FAT12 or FAT16. The new SDHC cards with Version 2.00 use the more up to date FAT32. This change was fundamental in allowing the SD cards to support the higher capacity needs of today's multi media devices.

Although the SDHC card uses the same electrical and physical form factor as SD, the SD 2.0 standard allow the SDHC cards to use a different memory addressing method. SD cards use byte addressing and SDHC uses sector addressing. This change in addressing method, theoretically allows a maximum storage capacity of up to 2tb. Although the SDA have currently limited the maximum limit of SDHC card capacity to 32gb, there are already cards becoming available with 64gb and even more in the pipeline.

SDHC Memory Cards Vs SD Memory Cards

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