The first data was stored on cards as far back as the 18th century, but these punch cards which automated the weaving of fabrics were incredibly simple compared to the digital devices we use today.
Modern digital memory cards have become an integral part of life, serving as compact, reliable storage solutions for a myriad of devices, from cameras and smartphones to handheld gaming consoles and even unmanned aerial vehicles. The journey of memory cards is one of technological advancement, marked by increasing storage capacities, shrinking physical sizes, and rapid improvements in data transfer speeds.
Early Beginnings
All digital memory cards rely on flash memory which utilises electronic signals to store data. Invented by Fujio Masuoka in 1980 while working at Toshiba, the technology was commercialised in 1987.
The consumer story of memory cards begins in the early 1990s with the introduction of the first commercial memory card format, the PC card (Created by PCMCIA), originally designed for memory expansion in notebooks and laptops. These cards, while innovative for their time, were relatively large and not suitable for smaller devices (early laptops were notably larger than today). However, PC cards paved the way for the development of more compact and efficient storage solutions.
Growing in Number
The CompactFlash (CF) card, introduced by SanDisk in 1994, was one of the first formats to gain widespread adoption. CF cards were initially used in digital cameras and offered storage capacities ranging from 2MB to 10MB, which gradually increased to 1GB by the early 2000s. CompactFlash cards utilised a 50-pin interface and were known for their robustness and reliability, making them a favourite among photographers.
Following CF, the SmartMedia (SM) card was introduced by Toshiba in 1995. SmartMedia cards were thinner and lighter than CF cards but had lower storage capacities, peaking at 128MB. They found their niche in early digital cameras and MP3 players. The MultiMediaCard (MMC), introduced in 1997, was another significant milestone. MMC cards were about the size of a postage stamp and compatible with many devices, including mobile phones and digital cameras. However, their popularity waned with the introduction of more advanced formats.Collaboration and Standardisation
The introduction of the Secure Digital (SD) card in 1999 marked a major turning point. Developed by the SD Card Association (SDA) in a collaboration between Panasonic, SanDisk, and Toshiba, SD cards improved upon MMCs quickly becoming the industry standard due to their compact size, high capacity, and security features. SD cards evolved through several iterations:
– SD (up to 2 GB)
– SDHC (Secure Digital High Capacity, up to 32 GB)
– SDXC (Secure Digital Extended Capacity, up to 2 TB)
Each new version brought higher storage capacities and faster data transfer speeds, making SD cards the preferred choice for many portable devices including digital cameras.
Shrinking Form Factors
As mobile devices became smaller, memory cards needed to follow suit. Introduced in 2005, the microSD met the demand for miniaturised digital storage. Despite its diminutive size (15mm x 11mm), microSD cards can now store up to 2TB of data, making them ideal for smartphones, action cameras, and drones. microSD cards have also gone through similar evolutions as their larger SD counterparts, with microSDHC and microSDXC versions available.
Improving the Standard
SD cards have advanced significantly in speed and performance since their inception. The progression began with the introduction of speed classes, which denote the minimum write speeds, with Class 2 starting at 2MB/s and Class 10 at 10MB/s. This system was followed by the UHS (Ultra High Speed) classes: UHS-I (U1) and UHS-I (U3), which offer minimum write speeds of 10MB/s and 30MB/s, respectively. The latest development is the Video Speed Class (V6 to V90), designed for 4K and 8K video recording, offering write speeds from 6MB/s to 90MB/s.
UHS and Beyond
In recent years, further advancements have focused on improved efficiency between the card and compatible devices. The introduction of the Ultra High Speed (UHS) bus interface significantly boosted data transfer rates. UHS-I cards achieve up to 104MB/s whilst UHS-II increases this upper limit to 312 MB/s. The specification for UHS-III bus interface cards was released in 2017 and promises to offer up to 624MB/s data transfers, whilst only a year later SD Express specifications were released announcing speeds of up to 3940MB/s, but these technologies are still a work in progress with manufacturers as none have yet hit the open market.
Storage size has also improved. In 2018, SDUC (Secure Digital Ultra Capacity) was announced which will provide capacities up to 128TB when available in the market.
XQD and CFexpress cards, which leverage PCIe and NVMe interfaces, offer even higher speeds and capacities, catering to the needs of professional videographers and photographers who require rapid data access and large storage volumes.
New formats like Universal Flash Storage (UFS) promise to deliver even higher performance and greater efficiency, further pushing the boundaries of what is possible in data storage.