Base Memory; Extended Memory - Gigabyte GA-7VX User Manual

Memory
The category is display-only which is determined by POST (Power On Self Test) of the
BIOS.

Base Memory

The POST of the BIOS will determine the amount of base (or conventional)
memory installed in the system.
The value of the base memory is typically 512 K for systems with 512 K memory
installed on the motherboard, or 640 K for systems with 640 K or more memory
installed on the motherboard.
Other
Memory
This refers to the memory located in the 640 K to 1024 K address space. This is
memory that can be used for different applications.
DOS uses this area to load device drivers to keep as much base memory free for
application programs. Most use for this area is Shadow RAM.

Extended Memory

The BIOS determines how much extended memory is present during the POST.
This is the amount of memory located above 1 MB in the CPU's memory address
map.
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BIOS Setup