Thursday, May 27, 2010

About Secure Digital (SD) memory cards

Secure Digital (SD) cards are small memory card widely used in many portable devices nowadays.

The devices that use SD memory cards include digital cameras, mobile phones, PDAs, digital camcorders, GPS navigators, netbooks, media players, etc.

Beside being the data storage medium in those portable devices, SD memory cards is also a handy medium to transfer data from one to another. As such, newer computers, laptops, televisions, etc. also equiped with SD card reader to enable them display graphics and/or videos in the SD card onto their screen. Certain printers (including my Brother DCP-130C) also have SD card slot to print out images in the SD card directly.

SD memory cards come in 3 different physical sizes:
  • Standard SD - 32 × 24 × 2.1 mm
  • miniSD - 20 x 21.5 x 1.4 mm
  • microSD - 15 x 11 x 1.0 mm
Adapters are available, and usually sold together with the card, to convert smaller size card into larger one, such as from miniSD to Standard SD.

In terms of storage capacity, there are also 3 types:
  • Standard SD - up to 4GB
  • High Capacity (SDHC)  - 4GB to 32GB
  • Extended Capacity (SDXC) - 32GB to 2TB
Certain devices, especially the older one, don't support SDHC nor SDXC. And some even older devices only support standard SD up to 2GB only.

In terms of writing speed, you might find the SD memory cards labelled as:
  • Class 2: 16 Mbps (2 Megabytes ps)
  • Class 4: 32 Mbps (4 Megabytes ps)
  • Class 6: 48 Mbps (6 Megabytes ps)
  • Class 10: 80 Mbps (10 Megabytes ps)
The lifespan of SD memory cards, if used properly and handled with care, is normally around 100k write cycle or 10 years. That should be good enough for normal users.


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