Fujio Masuoka invented the first memory card while at Toshiba in 1980. It was commercialized in 1987. Numerous memory card formats from different manufacturers emerged during the 1990s. This was a response to the emerging demand for removable storage solutions for digital cameras, personal digital assistants, and cellular phones.
However, due to the presence of different formats, there was market confusion. These cards were also deemed impractical. SanDisk, Matsushita, and Toshiba collaborated and introduced a new format in 1999 as a result. This was the Secure Digital or SD Card. These three also formed the SD Association or SDA in 2000 to promote and create standards.
Several manufacturers eventually adopted the SD Card format. Further developments in the technology resulted in practical advantages. These include improvements in storage capacity and reduced physical footprint. The introduction of microSD in 2005 also marked the emerging dominance of the Secure Digital card format in the market.
Pros of Secure Digital Card: Advantages of SD Card and Notable Applications
1. Intended as a DRM Storage Solution
The Secure Digital Card format was derived from the MultiMediaCard standard. It was initially developed and marketed 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 content.
2. Provided a Universal Storage Format
The market for memory cards was inconvenient during the 1990s and early 2000s due to the presence of different formats. The Memory Stick was a proprietary format exclusive to Sony products. Other manufacturers licensed their own formats. This left the consumers with no other option but to purchase different formats for different devices.
However, because the Secure Digital Card has an open-source license, it was positioned as a universal card compatible across different platforms. This enticed widespread adoption among manufacturers. The format became an industry standard in 2005. This translates to cost-efficiency among manufacturers and convenience among end-users.
3. Storage Capacity and Small Footprint
The range of storage options is an advantage of SD cards. The full-sized version had capacities of up to 2 GB. Developments in transistor technology resulted in denser capacity standards. The SDHC of 2006 supported up to 32 GB. The SDXC of 2009 has a maximum capacity of 2 TB while the latest SDUC of 2018 can support up to 128 TB
Advancements in transistor technology enabled the design and development of smaller Secure Digital Cards over the years. These include the miniSD and the microSD form factors. Take note that microSD cards began dominating the market in 2008. These cards became the most ideal compact storage solution for consumer electronic devices.
4. Price Options Based on Performance
Affordability is another advantage of SD cards. A 64GB SDXC from an OEM is priced at around USD 5.00. Even Samsung Evo microSD cards have price points ranging from USD 5.00 to USD 10.00. A class 10 SDXC card with more than 500x rating and 1TB capacity has price points ranging from USD 300.00 to USD 500.00.
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. Consumers who are looking for backup storage would benefit from the cheaper and lower-class SD cards. Power-users could take advantage of the larger capacity and better performance of more expensive cards.
Cons of Secure Digital Card: Disadvantages of SD Card and Key Limitations
1. Limitations in Real-World Performance
The indicated speed class rating does not translate to actual performance. Different cards from different brands with similar ratings have different performance. Speed is dependent on hardware integrity, soft error frequency, data and file fragmentation, and flash controller capability. External cards are also slower than cards used for internal storage
Cards with lower ratings are also not 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 lower than class 6. Digital cameras that use slower cards would have noticeable delays in between recordings.
2. Notable Backward Compatibility Issues
SDCX cards are compatible with SDHC readers but these same SDCX cards are only usable in devices with SDHC readers if they are reformatted to the FAT32 file system. The exFAT is the suitable file system format. SDHC and SDCX would not run on older SDSC and SDHC readers. Full-sized and mini-sized cards will not fit in microSD card readers.
Then there is the different use-case logic behind storage capacities and speed ratings. A 256 GB card is unusable in readers meant for reading 32 GB cards. The same is true for 2 TB cards fitted in readers meant for 500 GB or below. Consumers must also be well-versed in the speed ratings. Class 6 or lower is not suitable for sustained throughput applications.
3. Short Lifespan and Hardware Integrity
An SD Card is based on non-volatile flash memory. 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. Branded cards have cycles ranging from 5000 to 10000. Nearing and reaching the limit would produce errors until the storage integrity starts to fail.
The small footprint and overall physical characteristics of these cards also affect their durability. Their thin profile means that they can break under a considerable amount of force. They are also prone to data corruption when not stored properly or unused for a long time. The fact that these cards are small also means that they are prone to misplacement.
4. Options from Different Manufacturers and Brands
Another notable disadvantage of SD Card is that its quality and performance are dependent on the technology and processes used in its production. The open-source nature of the format has enabled more manufacturers to produce their brands of Secure Digital Cards. This also means that different brands of these cards also have different levels of quality.
Unbranded cards from unknown manufacturers might be inexpensive but might not be as reliable as the branded and more expensive ones. Some cards from unknown manufacturers are also passed as branded products with counterfeited trademarks. Consumers must be vigilant to ensure that they are purchasing genuine cards from known manufacturers.
Pros and Cons of SD Cards: Advantages and Disadvantages of Secure Digital Card
The Secure Digital Card format remains ideal as an external storage solution. Embedded SD cards have existed. These cards utilize the standard bus interface and integrate one or more flash memory types and an SD memory controller in a single package. But eMMC, UFS, and SSDs based on NVMe remain the better options for internal storage.
Note that the Universal Flash Storage format remains the most popular internal storage solution used in smartphones, tablets, and other portable devices. It has a faster data transfer speed than SD Cards. Apple later demonstrated that an NVMe SSD is a better internal storage solution due to its better sequential write and sequential read performances.