What is a 4G SD card?

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Secure Digital (SD) card is a memory chip in portable format, the size of the postal stamp and credit card thickness. It is an energy memory, which means that the chip does not require the power to maintain data. SD cards are popular storage devices for digital cameras, camcorders, mobile phones, portable computers, personal digital assistants (PDA), game consoles and other mobile electronic devices. The 4G card indicates a card with four gigabytes (GB) capacity.

Not every device that supports SD cards will support a 4G SD card. Secure Digital Association (SDA) responsible for issuing specifications and standards for the Revised version 1.x Standard, which allows capacity of up to 4 GB. This was achieved by extending the length of the block on the card up to 2048 bits. The problem arises when an older product does not receive block length data when reading the card identity string, provided a less length of 512 bits, and thus the Misidentifying card as with a lower capacity.

4G SD card can also linkto a newer standard 2.0 SD high capacity (SDHC). SDHC cards have capacities between 4 and 32 GB. The 4 GB limit overlaps with the previous version 1.x. SDHC cards are printed "HC" under the SD logo. This designation will miss the standard 4G SD card.

The main difference between the 4G SD card and its cousin SDHC is that newer specifications 2.0 guarantees minimum data transfer speed (DTR). Standard cards (1.x version) begin to write zero speed data and work up to maximum speed, then the write process is close to completion, the speed decreases and finally reaches zero. This process results in an average write speed, which is many times less than the maximum speed to which the card is evaluated.

SDHC cards are assigned a classification (class 2, class 4, class 6, etc.) that indicate a minimum, guarantured, permanent write speed. The most common classifications follow in megabitts per second (Mbps) andMegabytes per second (MB/PS):

• Class 2: Guaranteed Minimum Writing Speed ​​of 16 Mbps (2 MB/PS)
• Class 4: Guaranteed Minimum Write Speed ​​32 Mbps (4 MB/PS)
• Class 6: Guaranteed Minimum Write Speed ​​48 Mbps (6 MB/PS)

Usually, faster cards are more costly than slower cards of the same capacity, but in some cases speed is not a luxury, but a request. For example, a digital camcorder that relies on a flash card (versus hard drive) will have to be able to write on the card very quickly to record film frames. If a slow card is used, the result will be lost data or running frames. Conversely, if the product can only support slower enrollment speed, buying a faster card will be a waste of money.

products are evaluated as their ability to write at a certain maximum speed and this specification can generally be found in manual. The product with an evaluation 13x correlates with the Class 2 SDHC card; While the evaluation26x would be connected to the SDHC Class 4 card and Class 6 cards support products rated to 40x. Using Class 3 cards in a device that only supports class 1 speeds does not cause the device to work faster.

While any product that supports newer SDHC cards is backward compatible and can read a standard 4G SD card, products produced for 1.X SD only will not be able to read 2.0 SDHC cards. SD Extended capacity (SDXC) is an even newer specification and picks up where SDHC ended up on the border of 32 GB. SDXC has a maximum capacity of 2 terabytes.