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Also known as shadow RAM, shadow memory is the essentially a duplication of the routines inherent in the basic input/output operating system or BIOS of a computer system. This duplicate or shadow memory reserve is then housed in a protected area of the systems random access memory or RAM, making it easy to retrieve the copy when and as needed. Depending on the type of operating system used, the shadow memory may be used at startup and at certain times during the operation of the device. Other operating systems do not require the use of this type of memory, and may even often users the option of shutting down the duplicate memory as a means of allocating resources elsewhere.
The purse of shadow memory is to protect the system from possible damage to the read-only memory (ROM) that is a part of the overall system configuration. Older operating systems usually included this particular feature as a means of copying the BIOS for easy retrieval when the system was turned on, and sometimes even when specific tasks were being performed during the session. While some of the newer operating systems no longer rely on this particular approach, it is not unusual for the standard settings on the system to allow for the creation of a copy of the BIOS and their storage in a secured area of the RAM. The benefit to keeping this function active is that in the unlikely event that the BIOS housed in the read-only memory is damaged in some manner, the copy saved in the RAM may be used to overcome the issue and aid in repairing the corruption.
Depending on the configuration of the shadow memory, it may utilize a considerable amount of resources or require only a small amount to function efficiently. Users who are well versed in altering settings can normally apply different methods relevant to specific operating systems to adjust the amount of random access memory that is used in housing the copied data bytes. This may be especially helpful if the computer system involved has a relatively low amount of memory to begin with, and there is a need to allocate more of that memory to running other programs.
While the use of shadow memory may be optional with some operating systems, there is a difference of opinion regarding whether the feature should be shut off or allowed to operate. Proponents see the continued use of this feature as a protective measure that may never actually be needed, but can be very important to system recovery in the unlikely event of a corruption of the BIOS. Others note that the newer operating systems have additional protections that further reduce the potential for this type of issue, rendering shadow memory more or less obsolete.