Fujio Masuoka at Toshiba invented the first memory card in 1980, and it was commercialized in 1987. The early 1990s until the late 1990s saw the emergence of several memory card formats from different manufacturers in response to the growing demand for removable storage solutions for digital cameras, personal digital assistants or PDAs, and cellular phones.
The existence of different memory card formats drew confusion among end-users. They were also impractical. However, a collaboration between SanDisk, Matsushita, and Toshiba resulted in the introduction of a new format in 1999: the Secure Digital or SD Card. These three companies also formed the SD Association or SDA in 2000 to promote and create standards.
SD cards gradually gained momentum due to the eventual adaptation of numerous consumer electronics manufacturers. Further developments in the technology resulted in practical advantages to include improvements in storage capacity and reduced footprint. The introduction of microSD in 2005 marked the emerging market dominance of Secure Digital card format.
Pros of Secure Digital Card: Advantages of SD Card
Fundamentally a DRM Storage Solution
The Secure Digital Card format was derived from the MultiMediaCard standard and was initially designed to compete with the Memory Stick format of Sony through the inclusion of digital rights management based on the Secure Digital Music Initiative. An SD card is fundamentally a DRM product similar to the Memory Stick.
DRM products restrict the use of proprietary hardware and copyrighted works. DRM storages specifically prevent reading, writing, and transferring of protected files and multimedia contents. The initial idea behind the development of the Secure Digital Card format was to protect the storage and distribution of digital music and other digital contents.
Provided a Universal Storage Format
There was product diversity in the memory card market during the 199s and early 2000s. But this created inefficiency and inconvenience. The Memory Stick from Sony was a proprietary format exclusive to Sony-branded products. Different manufacturers also sought a specific license for a particular card format. This leaves end-users with no other option but to buy different brands of memory cards for different consumer electronic devices.
However, the Secure Digital Card was conceived and introduced to provide a universal memory card format with cross-device compatibility. Because manufacturers began utilizing this format due to its open-source nature, it has soon become an industry standard beginning in 2005. This translates to cost-efficiency among manufacturers and convenience among end-users.
Storage Capacity and Small Footprint
A notable advantage of SD cards is that they provide a range of storage capacity options. The earlier full-sized version of this format had capacities of up to 2 GB. Several capacity formats emerged alongside developments in transistor technology. The SDHC format introduced in 2006 supported capacities of up to 32GB while the SDXC announced in 2009 supports up to 2TB. The latest SDUC standard first announced in 2018 can support up to 128TB.
Advances in transistor technology have also allowed the introduction of smaller Secure Digital Cards over the years. These include the miniSD and the microSD form factors. Note that the microSD cards began dominating the market in 2008. These cards demonstrated a compact storage solution for consumer electronic devices.
Price Options Based on Performance
Affordability is also another advantage of SD cards. A 64GB SDXC from an OEM costs around USD 5. Even a Samsung Evo microSD cards have price points ranging from USD 5 to USD 10 depending on the storage capacity. Note that different rating and speed class determines the price of a particular Secure Digital Card. A class 10 SDXC card with more than 500x rating and 1TB capacity has price points ranging from USD 300 to USD 500.
Data transfer speeds can range from 2.34 MB/s to 14.6 MB/s. Cards with higher transfer speeds and better ratings are more expensive by default. End-users who are simply looking for a backup storage would benefit from the cheaper and lower-class SD cards. Power-users could take advantage of the large capacity and performance of more expensive cards.
Cons of Secure Digital Card: Disadvantages of SD Card
Limitations in Real-World Performance
Note that the indicated speed class rating does not translate to actual performance. Different cards from different manufacturers may perform differently despite having similar ratings. Speed depends on factors to include the overall hardware integrity, the frequency of soft errors, fragmentation of data and files, and capability of the flash controller. Cards used as external storage are also slower than internal or primary storage.
It is also worth mentioning that cards with lower ratings might not be suitable in situations that require consistent or sustained data write throughput. Frame dropouts or corrupted video files are possible in high-definition video recording using an SD card with a rating of lower than class 6 might. Digital cameras with slower cards would have noticeable delays in between takes.
Notable Backward Compatibility Issues
SDCX cards are compatible with SDHC readers. But it is important to highlight the fact SDCX cards are only usable in devices with SDHC readers if they are reformatted to the FAT32 file system. despite the fact that exFAT is the ideal file system for these SD cards. Note that cards based on newer capacity formats such as SDHC and SDCX would not run on older readers such as SDSC and SDHC readers. In addition, full-size and mini-sized cards will not fit in readers designed for microSD cards.
Then there is the different use case logic behind different storage capacity and speed ratings. A 256GB card is unusable in readers meant for reading 32GB cards. The same is true for 2TB cards fitted in readers meant for 500GB or below. Consumers must also be well-versed in the speed ratings. As mentioned, class 6 or lower is not suitable for sustained throughput applications.
Short Lifespan and Hardware Integrity
The biggest drawback of flash memory and solid-state drives, especially when compared to hard disk drives, is that they have limited write-erase cycles. Remember that a Secure Digital Card is based on non-volatile flash memory. Branded cards have cycles ranging from 5000 to 10000. Each cycle results in the deterioration of the oxide layer of a memory cell. Nearing and reaching the limit would produce errors until the storage integrity starts to fail.
Furthermore, the small footprint and overall physical characteristics of these cards mean that they are not durable. Their thin profile means that they can break under considerable force. There are also vulnerable to electronic corruption when not stored properly. The fact that these cards are small means that they are prone to misplacement.
Options from Different Manufacturers and Brands
The open-source nature of this format has enabled more manufacturers to produce their brands of Secure Digital Cards, thus driving their price points. However, note that a notable disadvantage of SD cards is that their quality and integrity would depend on the technology and processes employed by particular manufacturers.
Unknown manufacturers and unbranded cards from OEMs might not be as reliable as branded ones. There are also counterfeited cards. These cards are essentially produced by unknown manufacturers and passed as originally branded using counterfeited trademarks. Consumers must be vigilant to ensure that they are buying genuine cards.
SD Card is Not An Ideal Internal Storage Solution
The Secure Digital Card format remains ideal for external or removable flash storage. Embedded SD cards have existed. These cards utilize the SD standard bus interface and integrate one or more flash memory types and an SD memory controller in a single package. However, eMMC, UFS, and NVME-based SSDs remain the better options for internal storage.
Note that the Universal Flash Storage format remains the most popular internal storage solution used on smartphones, tablets, and other portable devices. It has a faster data transfer speed than SD cards. Apple eventually demonstrated that NVMe storage is a more internal storage solution due to better sequential write and sequential read performances.
