Owner`s manual

EMS expanded memory space is not linear, but addressed
through 110 port-controlled memory addresses called pages.
This means that on the EMS board, data is divided into
16KB pages, and then mapped into a 64KB address space of
the CPU memory called a window. By varying the page
number register, anyone of the 16KB pages in a 2048KB ex-
panded memory space can be mapped into this window.
Figure
12 shows how this mapping is done .
66
1024 KB
_____ ~1 ~~) _
64K lONE 16-KB
WINDOW PAGE
640KB
o
BASE
MEMORY
..----, 2048 KB
(2 MB)
-m
3~ _1------;
PHYSICAL
PAGE
L...-_~ OKB
PC ADDRESS MAPPING EMS
SPACE REGISTERS MEMORY
Figure 12: EMS Page Frame Addressing