A beginner's guide to SD cards

A beginner’s guide to SD cards

Between the burgeoning dotcom sector and fears over the Y2K bug, 1999 was a highly eventful year for technology.

Consequently, few people paid much attention in August when the Secure Digital memory card standard was unveiled.

A three-way collaboration between Panasonic, Toshiba and SanDisk, the SD Card Association established standards for compact and portable storage media.

SD was originally intended to rival Sony’s new Memory Stick format and Toshiba’s established SmartMedia cards. In time, both would be supplanted by it.

Primarily intended for digital cameras, there was little to suggest SD cards would become so vital for data storage on mobile phones, which were extremely basic at the time.

Yet today, they provide a simple, cheap and portable storage solution for smartphones.

So what do you need to know about them?

Size isn’t everything

Technological advances since the Millennium have seen three generations of SD card being marketed:

  1. SD. The original cards measured 32mm by 24mm, resembling a postage stamp with a tiny diagonal nick along one corner.
  2. miniSD. Having shrunk to 21.5mm by 20mm, these cards widened down one side to prevent incorrect insertion, with 11 metal contact points instead of the original’s nine.
  3. microSD. Measuring just 15mm by 11mm, microSD cards have a notch on one side – which also narrows as it approaches eight exposed contact points.

As is often the case, these devices have simultaneously become smaller and more powerful.

Original SD cards held as little as 1MB of data, whereas microSD devices could theoretically host 128TB – 128 million times more information.

Today, the maximum achievable storage capacity is 2TB, utilising the Secure Digital eXtended Capacity (SDXC) format.

For most smartphone users, a 64GB or 128GB card should be quite sufficient.

A 128GB microSD card can be purchased from leading online retailers for around £20.

Why are they commonly used in smartphones?

Because of their compact size, impressive storage capacities and innate portability, they’re ideal for inserting into smartphones to augment existing internal storage.

Since an average JPG or MP3 file occupies around 5MB of space, a 64GB card will clearly provide generous storage for media files and downloadable content.

Saving files onto an external storage device means smartphone manufacturers can install smaller hard drives, freeing up capacity for operating systems and programs.

SD storage also enables users to eject a card from one device and pop it into a replacement handset, giving instant access to personal files.

Key points

It’s important to note that phone identity and address book contacts aren’t saved onto SD cards. Instead, key device data goes onto SIM cards supplied by your network operator.

SD storage is also exclusive to Android handsets, since Apple doesn’t incorporate SD slots into its devices.

If you fill your iPhone’s storage, your only options are to delete existing content, or upload data into the cloud (specifically Apple’s proprietary iCloud) using WiFi.

For everyone else, an SD port means you can buy a cheaper handset with a smaller hard drive, without compromising your ability to download and save content.

You don’t need to worry about whether a card is SDHC or SDXC, since the primary difference involves capacity – the former go up to 32GB, while the latter start at 64GB.

Cards also carry a speed classification – Class 2 writes data at 2MB/s, for instance.

As is often the case, faster is generally better.

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