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Should I have BIOS shadowing on?
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Are the acronyms confusing? try the Glossary of computer terms |
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The code which tells the computer how to access the video card is stored on
the video card itself in a ROM (Read Only Memory) chip. When the computer
wants to access the video card, it uses the video BIOS (Basic Input/Output
System) routines on the ROM chip(s). The only real problem with this is
that ROM chips run more slowly that traditional DRAM which is used for main
system RAM. As a result, most (if not all) modern BIOS setup utilities
(sometimes referred to as CMOS) allow the video BIOS to be copied to a
section of main system DRAM (this is the shadowing). This has the benefit
of speeding up video operations between the CPU and video card because the
video BIOS 'instructions' can be read more quickly from the shadow RAM, and
the disadvantage of using a relatively small block of upper memory (the
chunk of memory is located above 640k and below 1 Meg).
When video BIOS shadowing is turned off, some systems and memory managers
allow you to use that chunk of memory to load TSR's (i.e. mouse driver,
cdrom driver) which may allow you to free up some additional conventional
memory. When turned on, video operations will be performed faster, at
the expense of a chunk of upper memory. Unless you're tight for upper
memory or have a compatiblity problem, try running with shadowing on.
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