Evolution of the MicroSD

All Android devices uses SD cards in some way. For mobile devices this can be either standard SD or microSD. The standard SD isn’t quite standard anymore with the advent of SDXC. MicroSD, MiniSD or TF and TransFlash all refer to the same microSD cards used in mobile phones. In the past SD and MMC cards were compatible with one another when used in cameras. But this similarity does not mean RS-MMC and microSD standards are interchangeable. The SD and MMC union had went through a divorce because the read/write rate didn’t suit one another.


The different speeds is a real confusion. Class 4 is the most basic but let me assure you that they are all compatible with your Galaxy Note or IIs. In digital cameras, we are told to carry and use only the faster SD cards such as Class 6 and above.

Class 4 has a 4MB speed while a Class 6 has 6MB speed. This again confuses people because this speed does not denote it is a throughout put for read and write. Often the READ speed is faster while the WRITE speed is slower. The Class definition refers to the WRITE speed, that a Class 4 can achieve up to 4MB/sec WRITE speed.

Class 10 is the fastest, giving you speeds of up to 10MB a second. Lately, we have been seeing the disappearance of Class 6 microSD cards from stores and for good reason. The manufacturing cost of Class 6 and Class 10 cards are so narrow that manufacturers now refuse to make Class 6 cards totally and making the jump to Class 10. Thus Class 10 and Class 4 are defacto standards of choice.

There is a significant price difference in price between Class 4 and Class 10. Some soothsayers and naysayers will tell you that the Class 10 will be best for you but this is often not the case and will depend on your needs.

Class 10 is more suitable for tablets as the file sizes are often much larger, thus requiring a faster write speed. This is on the assumption that the files saved to a full screen, such as a graphic file, will be larger in real estate size than one saved on a smartphone.

Beyond this, there is the question of storage handling, where an app actually saves on the microSD card and not the USB storage and to pull this app out from its hiding place, you will need a faster card.

I used an app called SD Tools to check the read write speed of my Class 4 microSD card used on my Galaxy Note and the results were quite surprising. The WRITE speed was clocked at 3.9MB/sec while the READ speed was 10MB/sec.

All this sounds fine on paper and when I test the SD card with movies, by storing a HD movie on my card, I realize that there was no frame drops or stutters even with a slower card.

10MB/sec is more than sufficient to deal with movies and I suspect that the rumors of a Class 4 underperforming are unfounded.

UHS-1 microSD from Samsung

Android has a weird way of segmenting and using storage. Persistent apps which needs to get online to fetch updates occupy a segment of the RAM. Some part of the app can be moved to mircoSD storage. Your camera app can be made to save to microSD on some Android devices.

This means you will need a much faster card to go with the high resolution pictures. Samsung has just announced its ultra high speed capable of Class 20 speeds. These cards are suppose to be backward compatible to the existing microSD standard but I can’t confirm it as the press release is a little thin. Read speeds for these cards are claimed at 80MB/sec while write speeds are closer to 20MB/sec.

Lastly, rooted Android devices can be made to set the data cache at a much higher rate allowing for faster transfer speeds between device and microSD but this only works with a faster card. With the current crop of SD cards already running at Class 10, you are not left with much of a choice since the Class 4 cards can’t be prodded to run any faster than an old dog.

I am still not sold on the speed requirement as it is device dependent. Not all Android devices come with generous internal storage, this is true for cheaper smartphones and Android devices running Froyo 2.2. The newer Gingerbread devices come with up to 1.8 GB of internal storage.

Devices without such internal storage would have to install directly onto a microSD card necessitating the use of a fast microSD card. So before you jump to eBay to look for these new fangled microSD super cards, please read your phone specification list and look for the following:-

  • Internal Storage
  • RAM
  • ROM
  • microSD
Most apps on Gingerbread will not be moved to SD card as you would believe but to the Internal Storage. This Internal Storage is also called USB storage and causes heaps of confusion in the process. So if your device is lacking a Internal Storage specification, then you should be in the market to get a Class 10 microSD card.

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