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SD or Micro SD memory cards, what to consider when shopping?



SD or Micro SD memory cards, what to consider when shopping?

Most devices are compatible with memory cards, either in the SD or Micro SD format, and usually among their features will tell you that they are compatible to some extent, but also depending on the memory card details. Buying an SD or Micro SD that isn't compatible with your device can be a waste of money, but you'll also regret doing it if it doesn't work as it should, right?

What to consider when buying an SD or Micro SD card

All SD memory cards fit into all SD card slots (and the same goes for SD cards), but not all will work. There are four different ways these cards and different levels, and these are the ones that determine consistency.

There are three main methods, and you are certainly familiar with their names (SD, SDHC and SDXC for SD cards, as well as MicroSD, MicroSDHC and MicroSDXC for Micro SD cards). The fourth format is SDUC, announced in 2018 and is not yet available on the market, so we will build on these three available. Both SD and Micro SD are based on the same specifications, so we will describe one of them:

  • Micro SD– Has capacity of up to 2GB and works on any SD device.
  • MicroSDHC– Has power up to 32GB and works on hardware that supports SDHC and SDXC.
  • MicroSDXC– It has a capacity of up to 2TB and is only supported on hardware that supports SDXC.
  • MicroSDUC– Supports up to 128TB capacity, and you will need a compatible device as above.

Without the level, you have to think capacity supported by your device. For example, just because the camera supports MicroSDXC cards does not mean that it supports up to 2TB. Always look at the device specification to find out which limit is applicable, because for example Samsung Galaxy S9 smartphones support microSD up to 400 GB, not 512 GB.

Speed ​​and Ultra high Speed ​​standard

Phase within compliance is standard Ultra High Speed ​​(IHS), which is evident in the support of multiple SDHC and SDXC formats. It has a fast circuit that allows for high transfer speeds, and there are three versions: UHS-I (up to 104 Mbps), UHS-II (up to 312 Mbps) and UHS-III (up to 624 Mbps). If the UHS is compatible with any type, it is represented on the memory card itself.

In order to use this technology, you should not only buy a compatible memory card, but you should make sure that you support your device because otherwise it will be like killing flies with guns and you will be spending extra money. If your Hardware does not support UHS it will only work on 25 Mbps.

On the other hand, to keep up with speed, memory cards have what is called Speed ​​Class or Speed ​​class, represented by a number inside C (Class). This symbolizes yours average speed of megabytes per second


Here we find Grades 2, 4, 6 and 10, respectively 2, 4, 6 and 10 MB / s of low speed.

Inside the UHS we have Speed ​​Class, represented by a number inside the U (from UHS).

We only have 1 and 3 here, representing at least 10MB / s for U1 and 30MB / s for U3.

Finally we see «Video Speed ​​Category«, Which is similar to the low-speed sequence that has a memory card, which is important for video cameras and especially those that record in 4K resolution. This is represented by a number inside the V (video) and the numbers range from 6 to 90 as follows:

  • V6: minimum writing speed of 6MB / s.
  • V10: 10 MB / s.
  • V30: 30 MB / s.
  • V60: 60 MB / s.
  • V90: 90 MB / s.

Some manufacturers use another format for this, called «Working class«, What is the minimum typing speed when used in applications? Here we have only two types:

  • A1: A minimum random reading speed of 1500 IOPS, and a random writing speed of 500 IOPS.
  • A2: 4000 Read IOPS and 2000 Write IOPS.

A close relative

Some manufacturers display their memory cards using limited speed, which is displayed much faster than a CD. The initial CD transfer speed is 150 Kbps, so if the manufacturer tells you that their memory card has a speed of 100X, that means we are talking about 100 x 150 Kbps, that is, 15 Mbps.

How to identify the attributes of your SD or Micro SD

So far we have given you a lot of data, so let's see how you can see it.

Let’s take this Lexar Micro SD as an example that illustrates and breaks down the image above. From top to bottom left to right, the first thing we find is the speed associated with the manufacturer's logo, this time at 633X, so it tells us that the functionality of this memory card works. 633 x 150 Kbps, that's 94.95 Mbps.

After this we go to the right and see that it has the A2 symbol, which indicates that in the applications they have 4000 IOP reading applications and 2000 IOP read randomly. At the top right we have a C with 10 spaces, which indicates Class 10 and has a top speed of 10 MB / s. Underneath it, the U has 3 inside, corresponding to the UHS speed class (tell us at the same time that it complies with the process), with a minimum speed of 30 MB / s.

We go downstairs, in blue. First we get the capacity, 512 GB in this case, and then the format, the Micro SDXC. It also tells us about that V30 that its Video Speed ​​Class is at least 30 MB / s. Finally, I show the bus interface, this time compatible with UHS-I (up to 104 Mbps).

Gamer, passionate about video games, technologies, gadgets and everything related to the world of electronics.

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