Epson 7500 - Manual (Page 51)

Reserved memo y is addressable memory in the range 640KB to
1MB. Normally, a video card or option card must provide the
physical RAM for these addresses. The system can enhance its
performance by using 128KB of this extra memory as shadow
RAM. Some of the remaining memory may be available; see
Appendix A of the User’s Guide for information on how your
computer uses this memory.
Extended memo y is memory with addresses in the range 1MB to
the maximum system memory, and can be used only by the
following:
Certain operating systems, such as OS/2®
Some MS-DOS interfaces, such as Windows
Some RAM disk programs, such as VDISK
Some hard disk caching programs, such as SMARTDRV
Certain specially-written, protected mode MS-DOS
applications.
Most versions of MS-DOS include a standard extended
memory manager. If you are using MS-DOS, Windows, and
other compatible programs, it is best to use one of the memory
managers (such as HIMEM.SYS) that came with your software
because these memory managers have been tested and proven
reliable.
Most MS-DOS commands and application programs cannot use
extended memory directly. They need to use expanded memo y.
This type of memory allows some MS-DOS applications to get
around the 640KB limitation. You control expanded memory
with a memory manager (such as EMM386.EXE), which enables
the computer to use your extended memory as expanded
memory.
A-2 Using Memory