Apple IIe - Page 14

14
Apple
lie
Users
Handbook
Perhaps
the
most
important
component
on
the
main
board
is
the
65028
microprocessor.
As
shown
in
Illustration
1-2,
the
65028
microprocessor
is
located
in
the
center
of
the
main
board
just
below
the
seven
slots.
The
65028
is
a high
speed
version
of
its
predecessor,
the
6502.
The
6502
was used in
the
Apple
II
and
II
Plus.
The
65028
can
address
64K
of
RAM.
However
,
the
lie
has
incorporated
special
memory
banking
and
switching
techniques
to
allow
more
than
64K
to
be
addressed
.
Several
other
important
components
of
the
main
board
are
depicted
in
Illustration
1-2.
These
include
an
AY
.;;
3600
integrated
circuit
and
a
ROM
chip
that
are
used
to
encode
the
keyboard
characters.
The
main
board
also
includes
two
ROM
chips
that
contain
the
Applesoft
BASIC
interpreter
.
The
main
board
contains
an
MMU
integrated
circuit which
controls
memory
addresses within
the
lie,
and
an
IOU
integrated
circuit which
controls
the
built-in
input/output
features
of
the
lie.
Eight RAM
IC
chips
are
located
at
the
bottom
right of
the
main
board.
These
supply
the
lie
with
64K
of
RAM.
Expansion Slots
Towards
the
rear
of
the
main
board
are
located
seven
expansion
slots.
These
sl
ots
allow
additional
hardware
devices
to
be
installed
with
the
Apple
lie.
For
example,
an
expansion
card
is
available
that
enables
the
lie
to
run
the
CP/M
operating
system.
Also,
controller
cards must
be
installed
in
these
slots
to
enable
a
printer
or
disk drive
to
be
used
with
the
lie.
Notice
that
these
seven
slots
are
numbered
from 1
through
7.
In
the
Apple
II,
eight
slots
(numbered
0
through
7)
were
available.
Auxiliary Slot
Notice
the
large
expansion
slot
located
on
the
left side
of
the
main
board
. This
is
known
as
the
auxiliary slot.
If
your
lie
contains
the
80-column
text
option
,
the
80
column
text
card
will
be
installed
in this
slot.