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Volatile and Nonvolatile Storage Devices

  • Article

5/10/2007

The deployment of a bootable run-time image onto a device requires a file system on a storage device that has read/write capability. If the bootable storage device is also nonvolatile, the image can be stored locally if there is enough space. Many types of storage devices are available for embedded systems. In Windows XP Embedded, alternative storage devices are classified in the following major groups:

  • Volatile RAM-based read/write storage devices.
    Random access memory (RAM) mass storage is similar to nonvolatile flash memory. However, the memory content in RAM is persisted only through the use of a power source such as a battery. Typically, RAM write-only access time is as fast as read-only access time.
  • Nonvolatile read/write storage devices, such as Flash ROM or magnetic disk.
    Nonvolatile flash or RAM storage is considered a ROM device if the computer it is installed on is unable to write to the file system. The contents of the file system are preset at the time of manufacture.
    For more information, see Nonvolatile Flash Memory Storage.
    For more information about deploying a run-time image to CompactFlash, see CompactFlash.
  • Nonvolatile read-only storage devices, such as ROM or CD-ROM.
    Conceptually, random access memory (RAM) semiconductor mass storage is similar to nonvolatile flash memory. However, the memory content in RAM is persisted only through the use of a power source such as a battery. Typically, RAM write-only access time is as fast as read-only access time.
  • PCMCIA
    The Personal Computer Memory Card International Association (PCMCIA) bus standard allows you to boot by using any PCMCIA ATA form factor card device. Such devices offer various storage technologies, such as a physical hard disk drive, or solid-state nonvolatile storage.

Some storage requires temporary or permanent write-protection. Permanent write-protection typically occurs by a physical change in the storage medium so that it becomes a read-only medium. Temporary write-protection can occur by a physical lock on the storage medium; however, not all media have this capability. You can use the Enhanced Write Filter (EWF) to write-protect your media. For more information, see Enhanced Write Filter.

See Also

Other Resources

Deploy a Run-Time Image
Enhanced Write Filter
Design a Run-Time Image