A technique used to increase a
computer's speed by using high-speed
RAM memory in place of slower
ROM memory (RAM is about three times as fast as ROM). On
PCs, for example, all
code to control
hardware devices, such as
keyboards, is normally
executed in a special ROM
chip called the
BIOS ROM. However, this chip is slower than the general-purpose RAM that comprises
main memory. Many PC manufacturers, therefore, configure their PCs to
copy the BIOS code into RAM when the computer
boots. The RAM used to hold the BIOS code is called
shadow RAM.
