Flash Memory

Flash Memory

Modern day solid-state storage solutions come in various physical sizes and quantities and they are the same components that were once used for primary memory usage as RAM in motherboards. The older removable and non-removable flash memory mechanisms, Secure Digital (SD) and other memory cards and USB flash drive are some examples of solid-state storage solutions. All these technologies can store staggering amount of data in a minute form factor. Some of these products are being provided in innovative packaging to facilitate their convenient transportation, for example, keychain attachments.

Flash memory has offered low- to mid-capacity storage for devices for several years in the form of modules and PC Card devices. The term “flash” indicates their ability to easily alter the content of the memory with the use of electricity. Router and switches are examples of original flash memory being used in devices requiring a non-volatile means to store critical data and code that is used to boot the device.

Flash memory is used in various forms by Cisco Systems for storing its Internetwork Operation System (IOS). The IOS is accessed from flash while booting up and in some cases, throughout operation uptime and thus during configuration sessions of an administrator. The 10S, in case of lesser models, gets stored in compressed form in the flash memory device and then gets decompressed into RAM where it is used during configuration and operation. After the boot up process is complete, the flash memory is not accessed again in such cases, unless its contents are being changed, for example, an IOS upgrade. For similar tasks, some devices use flash memory in the form of externally removable PC Card technology.

In the subsequent sections, we will discuss about the most popular forms of flash memory, memory cards and USB flash drives.

SD and Other Memory Cards

For storing temporary and permanent digital information, modern day smaller devices need a removable solid-state memory. Now no one uses microfloppies in the digital camera. Mini-DVD and HDD, the most popular forms of video-camera media, have given way to solid-state multi-gigabyte models. Modern-day electronics and even the most contemporary digital still cameras have started using removal memory card in some form to store still images as long as they wish to. The Secure Digital (SD) format has made its mark as the most popular leader of this pack that also includes Multimedia Card (MMC) format. Both SD and MMC cards measure 32mm by 24mm. The slots for receiving them are often marked for both. Slightly thicker than MMC, SD card also has a write-protect notch with often a switch for opening and closing the notch.

Mobile phones are examples of smaller devices with an SD solution. MiniSD is slightly thicker than SD and measures 21.5mm by 20mm. MicroSD is even thinner and measures only 15mm by 11 mm. Both miniSD and microSD come with adapters to allow their usage in standard SD slots

Clockwise from the upper left, CF/Microdrive, SmartMedia, Memory Stick (bottom right) and MMC/SD are accommodated on these slots. For allowing different formats to be compatible with each other, the industry provides adapters or convertors. There are various other devices that allow access to memory cards. For example, in a standard front-access drive way, you can purchase and install an external 3.1/2″ form factor devices. Card reader connected via a USB. Such external card readers are available in various configurations.


Embedded Flash Memory

Embedded MMC (eMMC) is based on classic MMC flash card. It stands for embedded Multimedia Card. An eMMC drive can be permanently embedded on the primary circuit board of a cheaper or smaller mobile device. The eMMC drive can also be made bootable with its integrated controller logic. The eMMC drives were developed much later than the removable MMC card, but they lack firmware and fast interfaces such as SATA in SSDs. With the use of multiple flash chips as an array, SSDs outperform eMMC drives by a good margin.


USB Flash Drive

USB flash drives are very convenient and versatile devices that allow storage of large amounts of data in a very small factor. Several of these devices are just extensions of the USB connector of the host, they extend from interface without adding much to the width. Thus, USB flash drives are easy to transport in both laptop bags and pockets.


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