What is Secure Digital Memory Cards (Also know as (SD, SD Flash, SDHC)

Types of Card :-

Standard SD (Secure Digital Card )

High Speed SD (Secure Digital Card )

SDHC SD Card  (Secure Digital High Capacity)

Micro SD Cards (Micro Secure Digital Card, AKA - Transflash)

Mini SD Card (Mini Secure Digital Card)

There are different speed grades available from Memoryforless which are measured with the same system as CD-ROMs, in multiples of 150 kB/s (1x = 150 kB/s). Basic cards transfer data up to six times (6x) the data rate of the standard CD-ROM speed (900 kB/s vs. 150 kB/s). High-speed cards are made with higher data transfer rates like 66x (10 MB/s), and high-end cards have speeds of 150x or higher (Ultra SD Cards). Note that maximum read speed and maximum write speed may be different, with maximum write speed typically lower than maximum read speed. Some digital cameras require high-speed cards (write speed) to record video smoothly or capture multiple still photographs in rapid succession.

As of December 2005, most devices comply to the SD card specification 1.01, maximum speed of 66x. Higher speeds of up to 133x are defined by specification 1.1.

Some devices Pre-2005 may not comply with this specification use our online Digital Camera memory guide to ensure your card complies with this specification. Memoryforless.co.uk guide is based on manufacture recommendations and testing unlike many guides on the net.

The NEW SDHC Format Card :-

A new SD format, SDHC (Secure Digital High Capacity, SD 2.0), allows capacities in excess of 2 GB. SDHC uses the FAT32 file system which supports a higher data density than FAT16[10]. It uses the same form factor as SD, but the SD 2.0 standard in SDHC uses a different memory addressing method (sector addressing vs byte addressing), thus theoretically reaching a maximum capacity of up to 2048GB. SDHC cards only work in SDHC compatible devices, but standard SD cards work in both SD and SDHC devices. The SDHC trademark is licensed to ensure compatibility.[11]

In August 2007 Toshiba announced that they would be launching a 32GB SDHC car and an 8 GB micro SDHC card worldwide in January 2008. Toshiba also announced a 16GB version available in the last quarter of 2007.

A number of Key Features have been published for each:

1.SDHC Memory Card (High Speed Type) (1) Realizes maximum write speed of 6 MB per sec. (2) "Class 4” SD Speed Class, guaranteeing sustained data write at 4 MB/s. (3) Integrates highly secure CPRM copyright technology.

2. micro SDHC Memory Card (1) Realizes large 8 GB capacity in a micro SDHC Card. It can store 139 hours of music at a bit rate of 128kbit/s. (2) "Class 4” SD Speed Class, guaranteeing sustained data write at 4 MB/s. (3) Integrates highly secure CPRM copyright technology.

SDHC cards have SD Speed Class Ratings defined by the SD Association. The SD Speed Class Ratings specify the following minimum sustained write speed on to empty SDHC cards:

Class 2: 2 MB/s
Class 4: 4 MB/s
Class 6: 6 MB/s

SD and SDHC compatibility issues

As of early 2007, the simultaneous availability of non-standard 4 GB SD and 4 GB SDHC cards, and incompatibilities between SD and SDHC have caused confusion among various consumers looking to buy memory devices.

The following compatibility issues between SD and SDHC cards and devices can arise:

• Devices that do not specifically support SDHC do not recognize SDHC memory cards, if your does not state SDHC Capacity is compatible it will not function (Even if the the unit states it can use over 2GB in capacity if the unit is not now SDHC compliant no card over 2GB will function.
• Some manufacturers have produced 4 GB SD cards that conform to neither the SD2.0/SDHC spec nor existing SD devices. These cards may function in some none SDHC compliant devices, this was a mistake in manufacture and these units are NOT SDHC Compatible.

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