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sd cards

Discussion in 'The Lounge' started by samuelmaskell, Jun 12, 2009.

  1. samuelmaskell

    samuelmaskell Well-Known Member
    Thread Starter

    May 11, 2009
    Software Engineering Student
    hey guys,
    I bought an 8gb micro sd card for my magic the other day
    and then afterward thought "I should have looked online for a 16gb one"
    so now I'm think I'll probably return the one I got
    only problem is, the 16gb ones are all class 2
    but the one I got is class 4
    so my question, how much of a difference is this going to make?
    I'll probably just be using it for music and photos
    I have a 2gb card in there now from my old phone
    and I have noticed that it takes a little while to load the pictures
    but I don't know if that's because of the card or not
    and I can't find the class of it anywhere
    do they not class the non-hd ones?
    so anyway,
    is it worth having less memory at a faster speed?
    I don't have any need for that extra memory
    but obviously it would be nice

    thanks for your help,


  2. bungdung91

    bungdung91 Member

    May 22, 2009
    My personal experience has been the same.

    I've read that APPS2SD requires a class 4/6 card. However, I've been running it with a class 2 16GB without issues so far. Admittedly I have not moved the dalvik cache to the card. If this paragraph sounded like greek to you, then ignore it, this pertains to rooting and then transferring your application from the internal memory to your SD card.
  3. samuelmaskell

    samuelmaskell Well-Known Member
    Thread Starter

    May 11, 2009
    Software Engineering Student
    yeah I didn't really understand what you were saying..
    definitely haven't rooted my phone
    but that's okay

    thanks a lot guys =]
    I didn't realize it only affected writing speed and not reading speed
    really appreciate it
  4. justjimjpc

    justjimjpc Premium Member

    Nov 3, 2008
    Washington DC, USA
    This is what Wikipedia has to say ...
    Secure Digital card - Wikipedia, the free encyclopedia


    There are different speed grades available 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 200x or higher. SanDisk classify their cards thus: Ultra II denotes a minimum read speed of 15MB/s (100x), Extreme III denotes a maximum speed of 30MB/s (200x) and Extreme IV which delivers up to 45MB/s (300x). 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. Note that this requires a certain sustained speed, or else the video will stop recording. A high maximum speed with a low sustained speed will be no better than a low speed card in terms of recording. Higher speeds of up to 200x are defined by specification 2.0.

    Some manufacturers use the read speed in their X-ratings, while others use the write speed. One company that uses the write speed in its X-rating is Kingston.[5]

    The following table lists some common ratings and their respective minimum transfer rates.Rating Speed (MB/s) SD Class
    6x 0.9 n/a
    10x 1.5 n/a
    13x 2.0 2
    26x 4.0 4
    32x 4.8 4
    40x 6.0 6
    66x 10.0 6
    100x 15.0 6
    133x 20.0 6
    150x 22.5 6
    200x 30.0 6
    266x 40.0 6
    300x 45.0 6

    SD Speed Class Ratings

    SD Cards and SDHC Cards have Speed Class Ratings defined by the SD Association. The SD Speed Class Ratings specify the following minimum write speeds based on "the best fragmented state where no memory unit is occupied":[6]
    Class 2: 2 MB/s - 13x
    Class 4: 4 MB/s - 26x
    Class 6: 6 MB/s - 40x

    SD and SDHC cards will often also advertise a maximum speed (such as 133x or 150x) in addition to this minimum Speed Class Rating. One critical difference between the Speed Class and the maximum speed ratings is the ability of the host device to query the SD card for the speed class and determine the best location to store data that meets the performance required. "Maximum speed" ratings are quoted by the manufacturers but unverified by any independent evaluation process.

    On 21 May 2009, Panasonic announced new "class 10" SDHC cards, claiming that this new class is "part of SD Card Specification Ver.3.0"[3]. As of that date, the SD Association's Web site did not include information on this new class or new specification.

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