What is flash storage?

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If you’re shopping for an SSD or using memory cards for cameras, you’ll likely come across the term “flash memory.” But what is flash memory and how does it work? We will explain.

Flash Memory Origins

In the early 1980s, a team of engineers at Toshiba led by Dr. Fujio Masuka invented a new type of non-volatile semiconductor memory called flash memory.

Flash memory is a breakthrough because it has allowed fast rewriting and can store data without power. Being solid, it used no moving parts, so it was sturdy and durable, and required less power to operate than traditional magnetic disk solutions. Its low power requirements – and its small size – make flash memory ideal for portable devices.

According to the Computer History Museum, flash memory got its name due to its ability to quickly erase data – in a “flash”. Previous erasable, non-volatile solid-state memory chips (such as EPROMS) take minutes (sometimes up to 20 minutes) to erase before rewriting can occur. It was this speed of writing, erasing and rewriting that later made flash memory a viable alternative to floppy disks or CDs in the form of thumb drives and traditional hard disks in the form of hard drives.

Related: Even after 25 years, the Iomega Zip is unforgettable

How does flash memory work?

Flash memory consists of floating gate transistors, which store electrons on an insulated gate. The gate is electrically charged to carry electrons, and this charge can be used to represent data. Flash memory can be erased and rewritten because electrons can be removed from the floating gate, which resets the transistor to its original state. This is done by sending an electrical charge through the transistor which releases electrons from the gate.

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Flash memory comes in three basic formats: NOR, NAND (named for types of logic gates), and EEPROM. Today, most flash memory is of the NAND type because it is the least expensive and usually uses less power than other types.

Types of flash memory cards

Different types of flash memory cards
Different types of flash memory cards. Bing Edwards

Electronics manufacturers use flash memory in a variety of applications, including smartphone storage, USB drives, and solid state drives (SSDs). SSDs are becoming increasingly popular as an alternative to traditional hard disk drives. Solid state drives (SSDs) are faster, more durable, and use less power than spinning disk hard drives.

During the 1990s and 2000s, flash memory was frequently used by average computer owners in the form of removable flash media cards, often inserted into digital cameras and PDAs. Here are some of the main forms of flash media cards – including when they are presented and their maximum capacities:

  • compact flash: Introduced by SanDisk in 1994. Available in capacities up to 512 GB, and later extended with CF 5.0.
  • Smart Media: Introduced by Toshiba in 1995. The maximum capacity was 128 MB.
  • MultiMediaCard (MMC): It was introduced in 1997 by SanDisk and Siemens. Available in capacities up to 512 GB.
  • memory stick: Introduced by Sony in 1998. Available in capacities up to 128MB.
  • Digital Security (SD): It was introduced in 1999 by SanDisk. Supports up to 2 GB, and extended formats support up to 128 TB in theory.
  • xD-Picture Card: It was introduced in 2002 by Olympus and Fujifilm. Available in capacities up to 2 GB.
  • XQD card: Introduced in 2011 by Sony. Available with a data capacity of up to 4 TB.
  • CFexpress: It was introduced in 2017 by the CompactFlash Association. Available in capacities up to 4TB.

Many of these types of media cards have been expanded with new standards to support higher capacities over time, such as SDHC, SDXC, and MemoryStick Pro. Some flash media card formats also shipped in multiple sizes, such as miniSD and microSD, which remain compatible with each other through the use of adapters.

Related: What SD card do I need for my camera?

Flash memory life

As cool as flash memory is, it doesn’t have an unlimited life. In fact, it can only be written a certain number of times before it fails. However, in modern flash devices, the number of write cycles is rather large.

According to the SD Association FAQ, the life span of a consumer SD card is about 10 years. However, this can vary depending on the quality of the card and the conditions under which it is used.

Solid state drives (SSDs) usually last longer than flash memory cards because they are designed for heavy, continuous use. When shopping for an SSD, look for the “TBW” or “terabyte written” number. A higher number means that the drive can withstand more data written to it over time, and will generally last longer. If you are a regular home computer user, you don’t have to worry about SSD failing due to too many writes. But SSD hard drives fail randomly from time to time, so always remember to keep backups. Stay safe out there!

Related: What does “TBW” mean for SSDs?

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