Also known as shadow RAM, shadow memory is essentially a duplication of routines inherent in the basic input/output operating system or BIOS of a computer system. This duplicate or shadow memory reserve is then stored in a protected area of the system’s random access memory or RAM, making it easy to recover the copy when and as needed. Depending on the type of operating system used, shadow memory may be used at startup and at certain times during device operation. Other operating systems do not require the use of this type of memory and may even frequently use the option to turn off duplicate memory as a means of allocating resources elsewhere.
man holding computer
The purpose of shadow memory is to protect the system from possible damage to the read-only memory (ROM) that is part of the overall system configuration. Older operating systems often included this specific feature as a means of copying the BIOS for easy recovery when the system was 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 uncommon for default system settings to allow for a copy of the BIOS to be created and stored in a safe area of RAM. The advantage of keeping this function active is that, in the unlikely event that the BIOS housed in read-only memory is damaged in some way,
Depending on the configuration of shadow memory, it can use a considerable amount of resources or require only a small amount to function efficiently. Users who are well versed in changing settings can typically apply different methods relevant to specific operating systems to adjust the amount of random access memory that is used to store the copied data bytes. This can be especially useful 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 run other programs.
While the use of shadow memory may be optional on some operating systems, there is a difference of opinion as to whether the feature should be turned off or operated. Proponents see continued use of this feature as a protective measure that may never actually be necessary, but can be very important for system recovery in the unlikely event of BIOS corruption. Others note that newer operating systems have additional protections that further reduce the potential for this type of problem, making shadow memory more or less obsolete.