SD, SDHC, SDXC, microSDHC memory cards explained

Over the past decade or so portable data storage technology has dramatically improved. The are a myriad options available, many suited to specific needs or niche requirements.   Making a purchasing decision on for your data storage needs, may at first hand seem a complicated, especially if you are in the market for memory cards.

 Secure Digital (SD)

The humble memory card or Secure Digital (SD) card, as it is more widely know, has come along way since it’s release in August 1999. Back then Sandisk, Toshiba and Panasonic collaborated to improve the technology that was available in it’s predecessor the MultiMedia Card (MMC). While both cards shared the same physical card size, there were huge differences in the storage capacity.  The MMC was available in capacities of 128, 256 and 512 MB, when SD cards were initially released they could store up 2GB of data, based on the FAT16 filesystem. This was a huge leap forward at the time.

Secure Digital High Capacity (SDHC)

  • Class 2 : >=2MB/s TV recording / DVD/ standard DC
  • Class 4 : >=4MB/s Mpeg2 (HDTV)/ DC with continuous shooting
  • Class 6 : >=6MB/s Reflex DC and professional DC – on continuous shooting

Secure Digital Extended Capacity (SDXC)

In 2009, a further specification upgrade was released Secure Digital Extended capacity (SDXC), enabling further increased data storage capacity of up to 2TB and increased speeds of up to 300MB/s. SDXC standard also provides capabilites to increase bus interface speeds up to 104 MB per second for UHS-I and up to 312 MB per second for UHS-II, as well as UHS Speed Class.

SDXC’s extended capacity will provide more portable storage and offer greater speeds required to support new features in consumer electronic devices, mobile devices and industrial devices. It also gives consumers a valuable easy upgrade option, allowing them to add capacity as needed vs. replacing devices and creating more consumer electronic waste.

Gary Woodfine

Freelance Full Stack Developer at
Helps businesses by improving their technical proficiencies and eliminating waste from the software development pipelines.

A unique background as business owner, marketing, software development and business development ensures that he can offer the optimum business consultancy services across a wide spectrum of business challenges.