Memory Cards and Everything You Need to Know About Them

Memory Cards and Everything You Need to Know About Them

If you think that when buying memory cards for your gadgets, you need to look only at the supported format and volume, you will have to upset. There are at least five important points to consider.


Everythings To know About Memory Cards

Everythings To know About Memory Cards


For most people, microSD is just a form factor, but it’s not. You can easily insert any microSD card into the standard slot, but not every one of them will work, as the cards vary in many ways.

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In total, there are three different SD formats available in two form factors (SD and microSD):

  • SD (microSD)– drives up to 2GB, work with any equipment;
  • SDHC (microSDHC)– 2 to 32GB drives, powered by SDHC and SDXC devices;
  • SDXC (microSDXC)– drives from 32GB to 2TB (currently a maximum of 512GB), only work on SDXC-enabled devices.

As you can see, they don’t have interoperability. The new format memory cards won’t work on old hardware.



The manufacturer’s stated support for microSDXC does not mean supporting this format with any volume and depends on the specific device. For example, the HTC One M9 works with microSDXC but officially only supports cards up to 128GB inclusive.

Another important point is connected with the volume of drives. All microSDXC cards use the default exFAT file system. Windows has been supporting it for more than 10 years; in OS X, it has appeared since version 10.6.5 (Snow Leopard; in Linux distributions support, exFAT is implemented, but “out of the box” works not everywhere.


UHS high-speed interface

The UHS-enabled card logo is added to the I or II, depending on the version

SDHC and SDXC format maps can support the Ultra-High-Speed interface, which, with hardware support on the device, delivers higher speeds (UHS-I to 104MB/s and UHS-II 312 MB/s). UHS is back-compatible with earlier interfaces and can work with non-support devices, but at a standard speed (up to 25 MB/s).



Classifying the speed of writing and reading microSD cards is as complex as their formats and compatibility. The specifications allow you to describe the speed of the cards in four ways, and since manufacturers use them all, there is a lot of confusion.


High-speed class

The speed class marking for conventional cards is a digit inscribed in the Latin letter C

The Speed Class has a minimum speed of recording on a memory card in megabytes per second. There are four of them:

  • Class 2 – from 2 MB/s;
  • Class 4 – from 4 MB/s;
  • Class 6 – from 6 MB/s;
  • Class 10 – from 10 MB/s.

Similar to the markings of conventional cards, the UHS speed class fits into the Latin letter U

The MAPS running on the UHS high-speed bus have only two-speed classes so far:

  • Class 1 (U1) – from 10 MB/s;
  • Class 3 (U3) – from 30 MB/s.

Because the speed class designation uses a minimum record value, theoretically, a second-class card may well be faster than a fourth card. Although, if this is the case, the manufacturer will most likely prefer to state this fact explicitly.


Maximum speed

The speed class is enough to compare cards when choosing, but some manufacturers, in addition to it, use in the description of the maximum speed in MB/s, and more often even not the speed of writing (which is always lower), and the speed of reading.

Usually, these are synthetic tests in ideal conditions, which are unattainable in normal use. In practice, speed depends on many factors, so do not focus on this characteristic.


Speed multiplier

Another classification option is a speed multiplier similar to the one used to indicate the speed of reading and recording optical discs. There are more than ten of them, from 6 to 633.

The 1 x multiplier is 150 KB/s, meaning the simplest 6 x cards have a speed of 900 KB/s. The fastest cards can have a multiplier of 633 x, which is 95 MB/s.



It is right to choose a map taking into account specific tasks. The biggest and fastest is not always the best. In certain usage scenarios, volume and speed may be excessive.

When buying a card for a smartphone, volume plays a bigger role than speed. The advantages of a large drive are obvious. Still, the advantages of high speed on a smartphone are almost not felt because there are rarely recorded and read files of large volume (unless you have a smartphone with 4K video support).

Cameras that shoot HD and 4K video are another matter: both speed and volume are equally important. For 4K videos, camera manufacturers recommend using UHS U3 cards, HD – regular Class 10, or Class 6.

Many professionals prefer to use several smaller maps for photos to minimize the risk of losing all images in force majeure circumstances. As for the speed, it all depends on the format of the photo. If you’re shooting in RAW, it makes sense to spend on microSDHC or microSDXC class UHS U1 and U3 – in this case, they will reveal themselves to the fullest.



No matter how trite it may sound, buying a fake under the guise of original cards is now simple. A few years ago, SanDisk claimed that a third of SanDisk’s memory cards on the market were counterfeit. It is unlikely that the situation has changed much since then.

To avoid disappointment when buying, it is enough to be guided by common sense. Refrain from buying from untrustworthy sellers and beware of “original” card offers, the price of which is much lower than the official one.

Attackers have learned to counterfeit the packaging so well that sometimes it can be tough to distinguish from the original. It is only possible to judge the authenticity of a card with complete certainty after checking with special tools:

  • H2testw – for Windows;
  • F3 for Mac and Linux.


The quality

If you’ve already experienced the loss of important data due to a memory card failure for one reason or another, when it comes to selection, you’re more likely to prefer a more expensive card to a well-known brand than an affordable “noun.”

In addition to the greater reliability and preservation of your data, you will get a high speed and warranty (in some cases even lifelong).

Now you know everything you need to know about SD cards. As you can see, there are many questions you will have to answer before buying a card. Perhaps the best idea would be to have different maps for different needs. So you can take full advantage of the equipment and not expose your budget to unnecessary expenses.

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