Owner`s manual
Step Two: Selecting EMS
I/0
Port Address
Unlike
base
memory
and
extended
memory
spaces
on
the
A T,
expanded
memory
space
is
accessed
by
mapping
each
16KB
of
EMS-specification
memory
into
a specific
memory
address
that
is usable by
the
computer.
By
combining
a
large
amount
of
these
mapping
schemes
in
a contiguous
manner,
we
create
a 64KB
memory
address space called a
window, this is
how
a single 64KB window
can
access
up
to
two megabytes
of
EMS-specification memory.
To
determine
the
memory
address
where
this 64KB
EMS
110
port
will reside, you switch Positions
1-4
and
5-9
on
Dip-
switch
SW1 to
inform
the
computer
where
to
look
for
an
open
memory
area
to place the 64KB
EMS
110 port.
The
RAM
3000 Deluxe is factory
configured
to
use
EMS
110
port
addresses
Y258
(EMS
liD
Port
1)
and
Y268
(EMS
Port
2),
where
Y
can
be
0,
4,
8,
or
C;
you
can
configure
SW1 so
the
board
will use
other
port
addresses.
Table
6 shows possible
EMS
I/O
port
address selections.
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