Differences and similarities between MicroSD, MicroSDHC and MicroSDXC, what is the difference

It's hard to imagine life without mobile devices. Smartphones, tablets, MP3 players or smart watches accompany modern people every day. The more they are used, the more memory is required. Photos, videos, music, applications - the internal memory of devices fills up in the blink of an eye. Therefore, additional external memory is required.

A memory card is a popular tool that allows you to quickly and easily increase the memory capacity of your device, thereby allowing you to store more data. Depending on your needs, you can use cards of different capacities. The most popular memory cards now are 32 GB and 64 GB. The decision to purchase a specific model is made based on the equipment in which the accessory is planned to be used and how many gigabytes are required for comfortable use.

What are MicroSD, MicroSDHC and MicroSDXC

Micro SD flash drives are smaller copies of SD (Secure Digital Memory Card) flash drives. Such digital products appeared as a result of the development of mobile technology. Modern gadgets are compact in size, which has created the need to create small memory cards in “Mini” and “Micro” formats.

Standard SD flash drives are 3.2 x 2.4 centimeters in size, while MicroSD is 15 x 11 millimeters.

On mobile devices that provide slots for such drives, it is often indicated that such gadgets support other formats. That is, from the point of view of equipment manufacturers, these flash drives do not differ from each other. However, this opinion is wrong.

MicroSD

MicroSD was one of the first to replace SD. This flash drive has the following features:

• maximum capacity - up to 4 gigabytes;
• length - 15 millimeters;
• width - 11 millimeters;
• thickness - 1 millimeter.

Due to the fact that this card appeared a long time ago, MicroSD has a slow data recording speed.

MicroSDHC

Flash drives of the micro SDNS type are characterized by the same dimensions as the previous ones, but are distinguished by a large amount of memory, which reaches 32 gigabytes. Cards of this format cannot be read by devices designed for MicroSD or SD. This is explained by the fact that the information that is downloaded to micro SDHC is recorded in FAT12 or FAT16 formats. MicroSD only supports FAT32.

MicroSDXC

Micro SDHS are capable of recording up to two terabytes of information. Moreover, such flash drives differ in the same sizes as the previous ones. Due to the larger memory capacity on MicroSDXC, information is written faster. Data on such external media is formatted in exFAT.

About the format[edit | edit code]

SD card capacity 16

MB

This standard was introduced in August 1999 by Panasonic, SanDisk and Toshiba based on an MMC card and has become an industry standard. In 2000, at CES, Matsushita, SanDisk and Toshiba announced the creation of the SD Card Association.

SDHC[edit | edit code]

8GB
SDHC Class 6 card

SDHC

(English Secure Digital High Capacity) is a removable flash memory card that meets the SDA 2.00 specification introduced by the SD Card Association. SDHC was a development of the SD format, inheriting most of its characteristics.

The potential maximum capacity of SDHC cards has been increased to 32 GB. As a rule, the FAT32 file system is used to store information on cards of this type (FAT16/32 was used for SD).

Compatibility[edit | edit code]

SDHC cards are not compatible with devices that are designed to only accept SD cards. The key innovation for SDHC cards, which allowed them to exceed the capacity of 4 GB, was the introduction of sector-by-sector addressing (similar to hard drives), while conventional SD cards have byte addressing (like RAM) and, accordingly, with a 32-bit address can have a volume of no more than 4 GB.

Some devices (card readers, communicators, etc.), designed to work only with SD cards, can “learn” to work with SDHC after changing the software, if hardware support for these cards was provided by the manufacturer.

You should also pay attention to the implementation version of the SD card (SD 1.0 or SD 1.1). If you plan to use it in an old device that supports memory cards up to 2 GB, make sure that it is version 1.0 and not 1.1, otherwise failures will occur during formatting and when the memory card fills with information.

SDXC[edit | edit code]

512 GB SDXC card

In 2009, at CES, the SD Association introduced a new SDXC

(English Secure Digital eXtended Capacity), supporting cards up to 2 TB and using the exFAT file system.

The new specification also adds a four-bit data transfer mode for SDHC and SDXC cards - the so-called UHS (Ultra High Speed) bus with transfer speeds of up to 312 MB/s. UHS memory cards are also compatible with normal transfer mode.

SDXC-enabled devices provide support for legacy SD and SDHC cards. SDXC cards with a capacity of 64 GB or larger can be used in (read from and write to) SDHC devices if they are formatted with the FAT32 file system[1].

Operating system support[edit | edit code]

• SDXC cards use the proprietary exFAT file system developed by Microsoft. Official support for SDXC card readers and cards is announced for Windows Vista, Windows Server 2008, Windows 7, Windows 8 and Windows 10. To support exFAT in Windows XP, there is an update KB955704. Due to the end of support for Windows XP, the update may not be available on Microsoft servers.
• Support on Linux/UNIX is provided using the free exFAT driver running outside the kernel (FUSE)[2]. The driver is available in the repositories of most popular distributions. Users of other distributions are encouraged to build the driver from source. There is also a native implementation from Samsung, devoid of the shortcomings of Fuse.[3] Samsung's exFAT implementation was included in the experimental section of the 5.4 kernel.[4]
• The MacBook Pro, updated in 2011, also supports SDXC memory cards[5]. All new Apple devices running Mac OS X 10.6.5 or later support SDXC cards as long as there is a physical slot in the device.
• Android supports SDXC on the factory firmware of most flagships, while the rest, like Linux, require a Samsung driver.

Compatibility issues[edit | edit code]

microSD 64 MB/microSDXC 128 GB

Immediately after approval, the standard was criticized due to the fact that the standard file system for it is the patented exFAT. Its specifications are not freely available, nor is there a full-fledged free driver (at the moment there is a proprietary driver for Linux and Android for companies and OEM equipment manufacturers[6]). Therefore, SDXC cards cannot be used in free operating systems. Even if a fully functional driver for this file system is created through reverse engineering, its use may be illegal in some countries due to patents. If you reformat the card to another file system that is free and supports large storage drives and files (for example, ext4 or UDF), the card may lose compatibility with the devices for which it is intended[7].

SDUC[edit | edit code]

In 2022, the SD Association introduced a new SDUC

(English Secure Digital Ultra Capacity), supporting cards up to 128 TB and using the exFAT file system. The standard is described in the SD specification version 7.0[8].

SD Express[edit | edit code]

On June 27, 2022, the SD Association introduced a new class of SD Express memory cards in three varieties: SDUC 1 express, SDXC 1 express and SDHC 1 express (maximum capacity 128 TB, 2 TB and 32 GB, respectively). These cards use the PCI Express 3.0 interface and NVMe 1.3 protocol via the second row of pins (also found in UHS-II/III cards) to achieve speeds of up to 0.9 GB/s. express cards are backward compatible with UHS-I cards[9][10]. Externally, SD Express cards are marked “SD Ex”.

MiniSD and MicroSD[edit | edit code]

miniSD have been developed for miniature devices

measuring 20x21.5x1.4 mm and the smallest of all cards is
MicroSD
(formerly known as
TransFlash
,
T-Flash
or
TF
)[11] measuring 11x15x1 mm. There are adapters for MiniSD and MicroSD cards, with which you can insert them into any slot for a regular SD card. Some miniSD and microSD card readers can be inserted without an adapter.[12]

• Adapter from microSD to SD. Kind of a classic
• Adapter device from microSD to SD
• Adapter from miniSD to SD
• Adapter from microSD to miniSD
• Card reader (adapter) microSD - USB

microSD Express[edit | edit code]

In February 2022, the new microSD Express format was introduced at MWC 2022, which will increase transfer speeds to 985 MB/s thanks to the addition of PCIe 3.1 interface signals. New signals are transmitted through the second row of contacts added to the microSD. The cards will remain backwards compatible with traditional readers.[13]

Microcontroller[edit | edit code]

SD card device: U1 - controller, two microcircuits at the bottom - memory. The contact pads are located on the back of the board

The 24x32x2.1mm card is equipped with its own controller[14][15] and a special area that, unlike MMC, is capable of recording information in such a way that unauthorized reading of information is impossible, in accordance with the requirements of Secure Digital Music Initiative". This fact was reflected in the name of the standard (“Secure Digital”). To write to a protected area, a special recording protocol is used, which is inaccessible to ordinary users. In this case, the card can also be protected with a password, without which access to the recorded information is impossible; The card's functionality can only be restored by completely reformatting it and losing the recorded information.

Secure Digital cards (except MicroSD) are equipped with a mechanical[16] write-protect switch. In the “lock” position, recording information and, accordingly, deleting files and formatting the card is impossible, which helps avoid accidental loss of information. However, it should be taken into account that the actual write protection is not carried out by the card itself, but by the device using the card, and may not be implemented in it or may be intentionally absent. For example, autoloading of the resident CHDK program for Canon cameras only works when the card is write-protected.

In most cases, SD can be replaced with an MMC card. Replacement is usually not possible: SD is thicker and may simply not fit into the MMC slot.

Transmission system[edit | edit code]

Drive with combined SD and USB flash interfaces

Cards can support different combinations of the following bus types and transmission modes. SPI bus mode and single-bit SD bus mode are mandatory for all card types, as described in the next section. Pin numbering is the same for all sizes of SD cards and host devices.

• SPI Bus Mode:
  Serial Peripheral Interface is mainly used in microcontrollers. This bus type only supports a 3.3V interface. This is the only bus type that does not require a host license.
• Single-bit SD bus mode:
  Separate bus for command and data channels.
• Four-bit SD bus mode:
  Uses additional pins, some pins are reassigned. UHS-I and UHS-II cards require this mode.

The physical interface includes 9 pins, except that miniSD cards add two unrelated pins in the center and microSD cards do not share one of the two pins.[17]

Numbering of contacts for cards (from top to bottom):

MMC

, SD, miniSD, microSD.
There is a noticeable evolution from the oldest MMC format, on the basis of which SD was created. SPI bus mode

Single-bit SD bus mode

Four-bit SD bus mode

Description:

1. The direction is determined relative to the map. In = In, Out = Out.
2. DL = Two
3. e
   ) when the output is not connected either to the power supply or to the common wire (“open circuit”).
4. OK =
5. Pit = Eating, Drinking).

Energy consumption[edit | edit code]

The power consumption of an SD card depends on its speed mode, manufacturer and model.

During transmission, the power consumption of the cards can be in the range of 66-330 mW (20-100 mA at a supply voltage of 3.3 V). For cards created using TwinMos technology, the maximum power consumption in recording mode is 149 mW (45 mA). According to Toshiba technology, consumption ranges from 264 to 330 mW (80-100 mA).[18] Standby current is significantly lower: less than 0.2 mA (2006 microSD cards).[19] If there is data exchange for a long period, then there is a significant consumption of battery power in portable devices, such as smartphones, where the batteries have a capacity of 6 Wh (Samsung Galaxy S2, 1650 mAh @ 3.7 V)).

If the host device supports SDR104 or UHS-II bus speed mode, then modern UHS-II cards can consume up to 2.88 W of power.
The maximum power consumption allowed by the standard in the lowest power mode in the case of UHS-II is 0.72 W. Card power consumption depending on bus speed[20]

table of correspondence

The correspondence table allows you to understand what type of external media is suitable for a specific device. This information was collected based on the speed (there are 6 classes in total) of transferring data to a flash drive or a special coefficient, the unit of which is 150 kilobits per second.

Difference between MicroSD, MicroSDHC and MicroSDXC

The differences between these flash drives are summarized in a table.

In connection with the above, it turns out that the choice between XC or NS format drives comes down to determining at what speed the flash drive should write information, as well as how much capacity the memory card has.

Comparison

Due to the fact that these drives differ in the same dimensions, when comparing them, the following must be taken into account:

• the type of devices for which the drive is intended;
• information recording format;
• storage capacity;
• supported speed of information transfer and reading;
• the file system used.

Expert opinion

Karnaukh Ekaterina Vladimirovna

Graduated from the National University of Shipbuilding, majoring in Enterprise Economics

When purchasing, you also need to consider the types of card readers that are available. In addition, you should pay attention to the way the data is formatted, since some legacy systems do not recognize more modern ways of compressing information.

File system

It is important to note that cards have different file systems, and they are defined differently in operating systems. So SDHC is formatted in FAT32

So SDHC is formatted in FAT32

But SDXC has a more modern exFAT format.

What does this tell us? Yes, everything is simple, modern operating systems, for example WINDOWS (older than VISTA), will see both formats. But if you have an operating system lower, for example WINDOWS XP (some are still running it), some LINUX distributions, they simply may not see “XC”, you will need to download additional drivers. Please take this into account when operating.

How does speed differ?

As noted, MicroSD records data at speeds of up to 25 megabits per second, MicroSDHC - from 50 to 150 megabits per second. MicroSDXC drives are available in different formats, differing in characteristics. These flash drives can support the following speed standards (megabits per second):

• UHS-Ⅰ – up to 104;
• UHS-Ⅱ – up to 312;
• UHS-Ⅲ – up to 624.

Drives that support these speed standards are not used in mobile devices. Such cards are intended for video cameras and cameras.

UHS bus[edit | edit code]

UHS‑II MicroSD Card

Comparison of a UHS-II card with a regular one

UHS (Ultra High Speed) bus is a high-speed data exchange protocol introduced in versions 3 and 4 of the standard. The specification requires backward compatibility of UHS cards and controllers with earlier Normal Speed ​​and High Speed ​​interfaces.[21]

The UHS-I interface is defined in the technical description version 3.01. Data exchange speed via the interface is 50 MB/s or 104 MB/s. Standard pins are used, but some pin assignments are redefined to accommodate 4-bit communication.

The UHS-II interface is defined in the technical description of version 4.00. Transfer speed - 156 MB/s or 312 MB/s. Cards of this standard contain two rows of contacts - 17 for a regular card and 16 for microSD; 4-bit exchange mode is used. In 2013, Panasonic, PNY and Toshiba introduced their first products using this technology.

UHS-II memory cards are used in photo and video equipment, high-end game consoles and other devices that require high data transfer speeds. Modern smartphones do not need UHS-II format.[22]

First or second generation - differences and advantages

The first and second generations of drives differ in capacity and recording speed. Also, these types of flash drives differ in the capacity of the system, the type of which has not changed.

Expert opinion

Karnaukh Ekaterina Vladimirovna

Graduated from the National University of Shipbuilding, majoring in Enterprise Economics

A more noticeable difference between these drives is visible when comparing first-generation memory cards and MicroSDXC, which support the specified speed formats. Such flash drives are even visually different from others. An additional row of contacts is provided on the body of these drives. Moreover, such cards can be used on devices intended for other flash drives.

But in such cases, drives write data more slowly. But the devices do not “slow down”. That is, the built-in operating system automatically slows down the flash drive.

The latest generation models stand out from the previous ones in that they are suitable for any modern mobile gadgets. However, in some cases, embedded operating systems do not recognize data compressed in the exFAT format. Therefore, before purchasing external storage media, you need to check whether the gadget you are using can read information from such devices.

Is the adapter a universal solution?

Since we can install a microSD card in a smartphone, it may be tempting to insert this card into a special adapter. This way we will get a full-size SD card, but it is worth leaving this option as a solution for a rainy day. The adapter will allow the microSD card to exchange data with the camera, but in this case the adapter itself takes on the role of the system bottleneck. Even the fastest card inserted into a hopeless adapter can offer much worse performance, not to mention the failure rate.

The second drawback of the solution is the fact that I mentioned earlier, namely the issue of card formatting. If a file system is optimized to work on one device, it will be extremely inefficient on another. Deleting and writing files leaves the card "empty" (i.e. generates fragmentation). The more such empty spaces, the less efficient the recording. Of course, if we have no other choice, it would be good to have an adapter with us as a backup. However, this decision should never be considered as the main one.

Although the above recommendations are general in nature, they will help you choose the best card. Of course, if you have any doubts about whether the memory you want to buy for a given device will work, I can recommend going to your last resort in these matters - the camera's instruction manual. Happy shopping!

Compatibility of the memory card with devices - which is better to choose

The selection of external storage media should be carried out taking into account the characteristics of the equipment used. For budget smartphones and players, it is recommended to purchase MicroSD drives. This is due to limitations in the data recording speed that similar devices have.

Expert opinion

Karnaukh Ekaterina Vladimirovna

Graduated from the National University of Shipbuilding, majoring in Enterprise Economics

For more modern smartphones and tablets that support shooting video in FullHD format, MicroSDHC is recommended. Such drives provide sufficient speed for writing and reading data. Mobile technology works without visible delays.

MicroSDXC drives are suitable for professional camcorders and cameras. It is not recommended to buy such flash drives for devices of other types, since all the advantages that these cards offer will be offset by the limitations of the gadgets. That is, in this case the difference between MicroSDXC and MicroSDHC will not be noticeable.

The characteristics of card readers should not influence the choice of digital memory chips. These readers are relatively inexpensive. Therefore, if necessary, the card reader can be replaced with a more modern one.

Form factor of Secure Digital memory cards

Let's start with the simplest thing - the form factor. SD Specification provides three sizes of memory cards:

• SD is a classic flash card with overall dimensions of 24x32x2.1 mm. One of the interesting features is the presence of a mechanical overwrite protection switch. When set to Lock, it blocks the ability to write new files to the card, delete existing ones, or format it.

• miniSD is a more compact version of flash cards, measuring 20x21.5x1.4 mm and aimed at use in portable devices. Currently, cards of this format are practically not produced.

• microSD is the smallest SD card in existence, measuring only 11x15x1 mm. It replaced its predecessor miniSD. Currently, cards of this particular type are used in smartphones, tablets, MP3 players, cameras, video cameras and other portable equipment. By the way, microSD has another, now outdated name - TransFlash (T-Flash or TF).

In addition to those listed, there is another, unique form factor - nanoSD, introduced in October 2022 by Huawei. In size, these memory cards are completely identical to nanoSIM and have dimensions of 12.3 × 8.8 × 0.67 mm, that is, they are almost 45% smaller than conventional microSD. They were released simultaneously with the Huawei Mate 20 and Mate 20 Pro smartphones, which support work exclusively with this flash card format, as well as with proprietary dual-port (USB + Type-C) card readers that allow you to work with other models of mobile devices, desktop computers and laptops .

Unfortunately, the only trump card of the new cards is their miniature size, while in terms of price and technical characteristics they are significantly inferior to classic microSD. For example, a Huawei Nano SD with a capacity of 128 GB and a sequential read speed of 90 MB/s costs almost 6 thousand rubles in the official store. For comparison,

Sandisk Extreme

of a similar capacity, with much more impressive characteristics (read/write speed up to 160/90 MB/s, respectively, with protection from water, high and low temperatures, shock and X-ray radiation) will cost you 2200–2500 rubles, according to Yandex. Market" (the information provided is current at the time of writing).

Since the new format has not yet been agreed upon by the SD Card Association and has not received official status, it is too early to talk about its further distribution. And in light of US sanctions against Huawei and the trade war with China, the prospects for nanoSD are becoming even more cloudy.