(Secure Digital High Capacity) is a standard for flash memory cards (including smaller versions - miniSDHC and microSDHC) used in cameras, cell phones and other devices.

Despite the complete external physical identity of "regular" SD (without "HC") cards, SDHC cards can only work in those devices where SDHC compatibility is explicitly declared by the manufacturer, while for such devices the full compatibility with "regular" SD cards. Some of existing devices that only support "regular" SD can acquire SDHC support thanks to new firmware.

SDHC differ from their predecessors by a modified addressing scheme and the use of the FAT32 file system, due to which the maximum capacity of SDHC cards produced is 32GB. However, this file system has an unpleasant property - the maximum size of a recorded file cannot exceed 4GB. Later, with the advent of SDXC, this problem was solved by switching to the exFAT file system.

The minimum size of SDHC cards is 4GB, "regular" SD cards of this size are in direct violation of the SD standard and have limited compatibility. Any device with SDHC support supports corresponding cards of any size.

Also for SDHC, the concept of “class” has been introduced, its numerical value is equal to the minimum steady-state recording speed on a given card (the most important speed characteristic of such products, it can affect, for example, the burst shooting speed of some cameras.) "SDHC Class 10" means that data can be written to such a card at a speed of at least 10Mb / s.

(Secure Digital eXtended Capacity) - the next version of the standard with a maximum card capacity limit of 2TB (two terabytes).

The intermediate version of the standard, also called SD 3.0 or UHS104, only describes cards with a capacity of 64GB and a maximum data transfer rate of up to 90 Mbps that can be compatible with some existing SDHC devices

The final version of SDXC, also called SD 4.0, raises the theoretical maximum data transfer rate to 300Mb/s, and the capacity of the cards can be higher than 64Gb. They are not fully compatible with SDHC devices.
SDXC-enabled devices also fully support SD and SDHC cards.
SDXC cards use the exFAT file system and officially support for card readers and SDXC standard cards is only announced for Windows Vista, Windows Server 2008 (the corresponding driver can be taken) and Windows 7. A set of drivers for Windows XP and Windows Server can be found. Mac OS X has supported exFAT since version 10.6.5. For Linux, there are proprietary solutions for working with this file system, embedding support for it in the kernel is scheduled for version 3.3.

SDXC cards use UHS classes to designate the write speed. On this moment there are two generations of UHS classes - UHS Speed ​​Class 1 (U1) from 10 MB/s and UHS Speed ​​Class 3 (U3) from 30 MB/s. The first one is enough for recording FullHD video, and the second one is enough for recording video in 4K format.

If you insert an SDXC card into a device that obviously does not support this standard, a message will be displayed asking you to format the card. In no case should this be done, since such an operation will render the card inoperable.

SD is one of the most successful flash memory standards on the world market today. One of its popular varieties is SDHC. Based on the appropriate technology, the world's leading brands produce sufficiently capacious and reliable memory cards. What are the features of this standard? How did devices supporting SDHC appear?

Specificity of SDHC cards

Cards SDHC memory(or Secure Digital High Capacity) are devices that operate according to a standard that has become further development SD technologies developed by the SD Card Association. The peculiarity of these devices is that their capacity can reach 32 GB. The file system most commonly used on these memory cards is FAT32.

One of the standards under which an SDHC memory card can be produced is micro. But in this case, along with the device, as a rule, you need to use an SD adapter, with which you can connect to a PC or other device that uses flash memory.

It usually comes bundled with a standard micro.

Compatibility

It should be noted that an SDHC-compliant memory card may not be compatible with devices that were originally designed to work with conventional SD cards. The fact is that it uses the principle of sector-by-sector addressing (as in hard drives), in contrast to the byte-by-byte one, which is implemented in memory cards of the previous generation.

Development history of SD cards

Before the world's IT engineers developed a memory card that supports the SDHC standard, this was preceded by a long and systematic work of the industry's leading brands to standardize and improve the manufacturability of flash devices used for file storage. So, in 1999, SanDisk, Toshiba, and Matsushita decided to create a new standard - SD, or Secure Digital. What was its specificity?

First of all, in support of DRM in accordance with SDMI criteria. In accordance with the concept proposed by the three brands mentioned above, the SD memory card format was supposed to compete with Sony's already well-known Memory Stick technology in the market. The three brands formed a new organization called the SD Assiciation. Subsequently, its structure included the largest brands - such as, for example, Intel, AMD, Samsung, Apple.

As part of SD technology, 4 main generations of flash cards have been released. The very first, operating on SD 1.0 technology, is capable of placing data in the amount of up to 2 GB, the second, SD 1.1, works within the file size of up to 4 GB. The limit value that characterizes an SDHC memory card is 32GB. The next generation of flash memory - according to the SDHX standard, can accommodate up to 2 TB of files.

SD-cards are used and those that support the SDHC standard in a wide variety of applications of digital technology. Appropriate devices can be used as carriers of almost any type of file. They are exceptionally productive in terms of use in photo and video equipment. SD cards are available, reliable. Devices operating on SDHC technology are also characterized by quite a decent capacity.

How did SDHC cards come about?

How did SDHC memory cards appear on the IT device market? The first devices operating in the SD standard, as we noted above, initially placed only up to 2 GB of data in themselves. For a long time, this resource was enough to perform basic user tasks - for example, placing documents, photos, music files.

Gradually, the needs of computer owners have increased. In 2006, a new, more advanced flash memory standard, SDHC, appeared. In the same year, SD Associations also developed several speed classes for related devices. Within each of them, the minimum speed value (in MB / s) for reading or writing files was fixed.

In general, they coped with the assigned user tasks. However, the needs of digital electronics enthusiasts have continued to grow. This is how the SDXC standard appeared, which involves placing files up to 2 TB. Although, it should be noted that such devices are rare in open sales and are expensive (it is usually cheaper to buy an external hard drive).

The file system installed on the latest SD cards is exFAT, which has become a further development of FAT32. Among the significant advantages of the new standard proposed by Microsoft is the reduction in the intensity of data overwrites within a single sector.

How to choose the optimal SD card?

In some cases, a PC user may be faced with the question of what is better to buy - SDHC memory cards or, for example, devices according to the SDXC standard? It all depends, first of all, on the required capacity of the device. Another criterion is the compatibility of a computer or other device with the corresponding standard. The fact is that old-style devices - cameras, PCs, card readers - do not always support flash memory released using the latest technology. At the same time, it is noteworthy that support for certain standards may depend not only on the hardware functions of the device, but also on the version of the firmware used on it. It may well be that a simple software update will help the device - for example, the same camera, learn to recognize the latest SDHC or even SDXC memory cards.

SDHC - Secure Digital High Capacity - is a removable flash memory card that meets the SDA 2.00 specification introduced by the SD Card Association (SDA), which unites about 500 manufacturers of flash memory cards. SDHC has evolved from the popular SD (Secure Digital) format, inheriting most of its characteristics. The potential maximum size 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 SDHC cards are not compatible with card readers and other devices originally designed only for SD cards. But devices that can work with SDHC cards also support SD cards. The key innovation for SDHC cards, which allowed them to exceed 4 GB, was the introduction of sector-by-sector addressing (similar to hard drives), while conventional SD cards are byte-addressed (like RAM) and, accordingly, with a 32-bit address can be up to 4 GB in size. Some devices (card readers, communicators, etc.), designed to work only with SD cards, after changing the software, can “learn” to work with SDHC, if the 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 made in version 1.0 and not 1.1, otherwise there will be failures when formatting and when filling the memory card with information.

Please improve the article in accordance with the rules for writing articles. In 2009, at CES, the SD Association introduced the new SDXC (eXtended Capacity) standard, which supports cards up to 2 TiB (2,199,023,255,552 bytes) and transfer rates up to 104 MB/s. In the future, it is planned to increase the speed to 300 MB / s. Of course, we are talking about the speed of the "card controller" interface<=>"reader controller", but flash memory is still far from such speeds, and it is its low speed that will determine the performance of the card as a whole. It is planned that the exFAT file system developed by Microsoft will be the standard for SDXC cards. Panasonic, Kingston and SanDisk introduced a 64 GiB SDXC card. Lexar introduced a 128 GiB card. The Japanese company Toshiba announced the release of 64 GB SDXC memory cards, which, according to the manufacturer, are the fastest cards in the world and have a maximum data transfer rate for writing - 35 Mb/s and 60 Mb/s for reading. In addition to the SDXC card, Toshiba has introduced two new models of SDHC memory cards, 16 GB and 32 GB, with the same speed as the SDXC card. New models of SDXC and SDHC memory cards, according to the company, comply with the new SD Ver. 3.00, UHS104 and are designed for use in devices that require large amounts of memory to store data at high data transfer rates, such as digital cameras and video cameras. The final version of SDXC, also called SD 4.0, raises the theoretical maximum data transfer rate to 300Mb/s, and the capacity of the cards can be higher than 64Gb. They are not fully compatible with SDHC devices. SDXC-enabled devices also fully support SD and SDHC cards. SDXC cards use the exFAT file system and official support for SDXC card readers and cards is only for Windows Vista, Windows Server 2008 and Windows 7. Other operating systems do not support SDXC at the time of writing the FAQ. SDXC support for Linux is possible for the foreseeable future. The updated 2011 MacBook Pro also has support for SDXC memory cards. Important note: If you insert an SDXC card into a device that does not support this standard, a message will be displayed asking you to format the card. In no case should this be done, since such an operation will render the card inoperable.

It is very easy to get confused in memory cards today: types, classes, different manufacturers and different formats make up the widest assortment on the shelves. Many users are sure that the main criterion for choosing a card should be its volume, and the price is of secondary importance. Well, the physical dimensions and design - the main thing is to enter the slot on the device. With a remarkable variety of drives, some people think that the card belongs to the SD type, and you can ignore the full name: speed, class, and novelty are ultimately not so important. However, despite the almost complete external identity and common tasks, SDHC and SDXC memory cards differ dramatically and may not be compatible with the device for which they were purchased. Let's try to figure out what the differences are.

Definition

SDHC is a flash memory card format that complies with the SDA 2.0 standard and is intended for use in mobile devices. SDHC is considered the third generation of SD.

SDXC is a flash memory card format considered the fourth generation of SD and conforming to the SDA 3.0 and SDA 4.0 standards.

Comparison

The consumer difference between SDHC and SDXC memory cards is the maximum possible amount of flash memory. For SDHC cards, the limit is 32 GB (with a minimum of 4 GB), for SDXC it is 2 TB (with a minimum of 64 GB). However, the last figure is impressive so far only theoretically: you still won’t be able to rewrite the collection of TV shows on one memory card for lack of one (as of July 2013). But the amount of 256 GB is already available, although the cost of such a card is equal to the cost of two or even three solid-state drives, each of which will provide the same volume. But we pay for compactness and mobility, so everything is quite fair.

Unlike SDHC cards, the SDXC format received two releases almost simultaneously. Compliance with the SDA 3.0 standard allows you to provide a volume of 64 GB with an average data transfer rate of 90 Mb / s. The SDA 4.0 standard assumes an incredible 2 TB of volume and 300 Mb / s. There is no SDXC less than 64 GB, so when choosing a memory card for the device, you should pay attention to the maximum limits declared by the manufacturer. 3rd generation SDXC cards may be compatible with some SDHC readers, 4th generation cards are not compatible with SDHC card readers. But card readers and other devices that accept SDXC will work fine with SDHC cards. Formatting an SDXC card in a device not designed for it will result in property damage, while SDHC is more resistant in this regard.

The key difference between SDHC and SDXC is in the file system. If the early format is formatted in FAT32 (as a rule, but not necessarily), then the exFAT file system has been created for the younger generation. The creator was Microsoft, so open operating systems work with SDXC does not shine in white - only after dancing with tambourines. Windows operating systems younger than Vista also do not support new standards without additional drivers, but for Mac OS X 10.6.5 and older an exception is made - the exFAT file system is accepted there along with the traditional FAT32.

Findings site

1. SDHC complies with the SDA 2.0 standard, SDXC with the SDA 3.0 and 4.0 standard.
2. The minimum amount of memory for SDHC is 4 GB, the maximum is 32 GB, for SDXC it is 64 GB and 2 TB, respectively.
3. SDHC cards are compatible with SDXC readers, not backwards compatible.
4. SDHC are usually formatted in FAT32, SDXC - in exFAT.
5. SDXC is not supported by all operating systems.

For most people, microSD is just a form factor, but it really isn't. You can easily insert any microSD card into a standard slot, but not every one of them will work, since cards differ in many ways.

Format

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

• SD (microSD) - drives up to 2 GB, work with any equipment;
• SDHC (micro SDHC) - drives from 2 to 32 GB, work on devices with support for SDHC and SDXC;
• SDXC (microSDXC) - drives from 32 GB to 2 TB (for this moment 512 GB maximum) only work on SDXC-enabled devices.

As you can see, they are not backwards compatible. Memory cards of the new format will not work on old equipment.

Volume

Support for microSDXC declared by the manufacturer does not mean support for cards of this format with any volume and depends on the specific device. For example, HTC One M9 works with microSDXC, but officially only supports cards up to and including 128 GB.

Another one is associated with the volume of storage important point. All microSDXC cards use the exFAT file system by default. Windows has been supporting it for more than 10 years, it has appeared in OS X since version 10.6.5 (Snow Leopard), exFAT support has been implemented in Linux distributions, but out of the box it does not work everywhere.

High speed UHS interface

I or II is added to the logo of a card with UHS support, depending on the version

SDHC and SDXC cards can support the Ultra High Speed ​​interface, which provides higher speeds (UHS-I up to 104 MB/s and UHS-II up to 312 MB/s) if the device has hardware support. UHS is backward compatible with earlier interfaces and can work with devices that do not support it, but at standard speed (up to 25 MB/s).

2. Speed

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Classifying the write and read speed of microSD cards is as complex as their formats and compatibility. The specs allow four ways to describe card speed, and since manufacturers use them all, there's a lot of confusion.

speed class

The speed class macro for ordinary cards is a number inscribed in the Latin letter C

The Speed ​​Class is the minimum write speed to the memory card in megabytes per second. There are four in total:

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

By analogy with the marking of conventional cards, the speed class of UHS cards fits into the Latin letter U

Cards operating on the high-speed UHS bus have only two speed classes so far:

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

Since the minimum value of the entry is used in the designation of the speed class, theoretically a card of the second class may well be faster than a card of the fourth. Although, if this is the case, the manufacturer will most likely prefer to state this fact more explicitly.

Max Speed

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

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

Speed ​​multiplier

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

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

3. Tasks

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Choose the right card for specific tasks. The biggest and fastest is not always the best. For certain use cases, 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 storage are obvious, but the advantages of a high transfer rate on a smartphone are almost not felt, since large files are rarely written and read there (unless you have a smartphone with 4K video support).

Cameras shooting HD and 4K video are a completely different matter: both speed and volume are equally important here. For 4K video, camera manufacturers recommend using UHS U3 cards, for HD - regular Class 10 or at least Class 6.

For photos, many professionals prefer to use several smaller cards to minimize the risk of losing all the pictures in force majeure. As for the speed, it all depends on the photo format. If you shoot in RAW, it makes sense to invest in microSDHC or microSDXC class UHS U1 and U3 - in this case, they will reveal themselves to the fullest.

4. Fakes

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

To avoid disappointment when buying, it is enough to be guided by common sense. Refrain from buying from untrustworthy sellers and beware of "original" cards that are priced well below the official price.

Attackers have learned how to counterfeit packaging so well that it can sometimes be very difficult to distinguish it from the original. With full confidence, it is possible to judge the authenticity of a particular card only after verification with the help of special utilities:

• h2testw- for Windows;

If you have already experienced the loss of important data due to a broken memory card for one reason or another, then when it comes to choosing, you will most likely prefer a more expensive card from a well-known brand than an affordable "no-name".

In addition to greater reliability and safety of your data, with a branded card you will receive high speed and a guarantee (in some cases even a lifetime).

Now you know everything you need to know about SD cards. As you can see, there are many questions that you will have to answer before purchasing a card. Perhaps, best idea will have different maps for different needs. So you can use all the advantages of the equipment and not expose your budget to unnecessary costs.