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FAQ: Understanding MicroSD & MicroSDHC Card Speeds – Class 6 & Class 4 Cards? Write & Read Speeds?

by Ronen Halevy on Jan 12th, 2009 at 4:00 pm EST
6 Comments »
 

sdassociation Shopping around for a new MicroSD card for your BlackBerry? Totally confused about what the difference is between a Class 4 and a Class 6 device? Wondering what 133x or 66x or 32x means?

Turns out that it is quite simple. The class defines the minimum write speed for a completely empty SD card. That means if you were writing to a new SD card that has never had any data on it how fast would it write.

  • Class 2 = 2 megabytes/second
  • Class 4 = 4 megabytes/second
  • Class 6 = 6 megabytes/second

So in short Class 6 is what you should be buying for fast write speeds. On top of this there is also the speed rating of the card itself. This is based on how fast the microSD card can READ the data off the card. You will see this usually described as 32x, or 66x, or 133x, or something with an x and the end. :)

These measurements are based on the original CD-ROM drives which could write 150kb/second. So 32x means 32 multiplied by 150kb/second or 4.8MB/second. This nice little table from Wikipedia gives you a basic idea of what each one stands for in terms of speed:

Rating Speed (MB/s)
6x 0.9
32x 4.8
40x 6.0
66x 10.0
100x 15.0
133x 20.0
150x 22.5
200x 30.0

Let me know if you have any more questions!

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This entry was posted on Monday, January 12th, 2009 and is filed under Accessories, BlackBerry FAQ.
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6 Comments to “FAQ: Understanding MicroSD & MicroSDHC Card Speeds – Class 6 & Class 4 Cards? Write & Read Speeds?”

  1. Posted by: Chris
    January 12, 2009 at 4:48 pm EST

    Thanks for the detailed info. I have an 8gb card in my Curve 8330. I don’t think a faster writing card would help. The curve still needs a faster processor :(

  2. Posted by: indroo
    January 12, 2009 at 6:14 pm EST

    What the different between SD and SDHC in relation to the read and write speed of those microSD card?

  3. Posted by: myers6mm
    January 12, 2009 at 9:24 pm EST

    I just read about this a week or so ago on Wikipedia, Here’s some more info http://en.wikipedia.org/wiki/Secure_Digital_card

    • Posted by: myers6mm
      January 12, 2009 at 9:29 pm EST

      Ok, nevermind my stupid comment! I just noticed the link in the article is the same as mine! Sorry!

      • Posted by: Ronen Halevy
        January 12, 2009 at 11:40 pm EST

        No worries. Just trying to spread the knowledge. May do another one about the difference between SD card and SDHC and also the difference between device RAM and Device Storage

  4. Posted by: DavidB
    January 13, 2009 at 7:29 am EST

    Right, but which Blackberry smart phones are capable of which Class is the question. If the device is only able to write at 2, spending the extra for a 4 or 6 is a waste, no?
    Given price parity, of course just buy the faster. But it would be nice if RIM would upgrade their capacity FAQ by adding max write speed each hardware supports.

    And don’t forget the new SDXC if you’re gonna write about cards!