Slow Phone or Tablet Performance - Check your SD card speed rating

Speed is everything in memory chips. Recently, SD cards came out with a speed rating based on the original CD-ROM speed (1.2Mbs) being read by the Optical Drive reader. Heres what to look for:

The speed rating 

Classes of Speed

Class 2:  Rating: 13x  Read: 16  Write:  16 

Class 4:  Rating  26x  Read: 32  Write:  32

Class 6:  Rating  40x  Read: 48  Write:  48

Class 10:Rating  66x  Read: 80  Write:  80

Be careful with some chips as the speed rating is loosely interpreted. Manufacturers might rate their speed based on read which is faster. Write is slower and should be the default speed for rating the chips performance. Kingston certifies on their write speed.

Your phone or other device will benefit from the speed difference with the type of chip you purchase. Your phone scans the media for data each time it boots.  A higher speed card will result in faster boot times and program load times.


SD Cards were an issue with the release of the Windows 7 phone from Microsoft as the chips were not fast enough for the phone. Article about SD Card limitations in Windows 7 Phone There are some reports a Class4 card will work.

The Windows 7 Phone will reformat the card and lock it to the phone and assign it a special key. It is not to be removed and is to be treated as permanent storage for your phone. So get a fast big one and stick with it. 


I was using a generic Class2 16GB card in my ATT Capivate Android with rooted Firefly 2.5.  Booting was slow, typing was sluggish as I used APP2SD with UltraKeyboard. Essentially, My Class2 SD card was killing the speed of my phone. My class 2 was performing like a 4200rpm hard-drive in my laptop. I had enough.


This week, I purchased a Lexar 16GB Class6 card. The card includes a full size SD adapter. I popped the SD card in my PC and copied everything to a temporary directory. I switched out the microSD to the 16GB Class6 and copied everything in my temp folder back to the new card. Rebooted my Captivate Android and the sluggish issues have disappeared. The phone boots faster. The card is scanned much quicker at boot (Media scanner running, Media scanner complete), the keyboard lag is non-existent. Apps now respond much quicker. I now feel like I just installed a 7200 rpm hard-drive. My dream storage at the moment is a Lexar 32GB Class 10 with write speeds of 10Mbps and read speeds of 20Mbps. Lexar gave the card a 10 year warranty! BGR Lexar Announcement.


Interesting Company from Taiwan - manufacturer of very fast memory cards:


Pretec, a Tiapei,Taiwan based manufacturer of small form factor memory cards, just released a Class 16 Speed Card for HD video. The card is a 64MB SDHX chip. They also released the worlds first USB 3.0 card reader.


MicroSD is created by Sandisk. All registered trademarks are respected.