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The
memory
information
in
CX
and
DX
is
used by
the
internal
operating
system
to
initialize
the
file
system
during cold
start.
The
address
in
DS:BX
points
to
a
table
of
segment
addresses which
give
the
base addresses
of
each
separate contiguous
ROM
region
in
the system.
On
cold
start,
this
is
used
to build
the
initial file
directory.
On warm
starts, this
is
used
to
detect
removable
ROM*s
which have
been
removed,
or
have
different
rom's
installed.
Note,
that
if
during a
warm
start
resume,
the
O/S
detects
that
there are
different
ROM's
present
in
the
machine
than
when
the
power
was
turned
off,
the
O/S
will
force
a
warm
start
break
operation
to
occur.
The
structure
of
this
table
is
as
follows:
count
region
1
Number
of
ROM
regions defined
Segment
address
of
the
first
ROM
region
region n
-
Segment
address
of
the
last
ROM
region
Power
On
Operation
Power-on
mode
Key combination
Value
of
Reg.
AL
Cold
Start
LABEL +
ALT +
BKSP
4-
power-on
AL
=
Warm
Start
Resume
no-key
-f
power-on
AL=1
Warm
Start
Break
SHIFT +
PAUSE
+
power-on
AL
=
2
Warm
Start
Alarm
(Auto
Power
On)
AL=3
Warm
Start
Auto-Answer
(Auto
Power On)
AL
=
4
Boot Uncooperative
System
LABEL +
ALT +
ESC
+
power-on
AL
=
5
(Hold
key
after
power-on,
and
release
it
a
little
bit
later)
The
feature
of
the
Boot Uncooperative
System
loads
the
boot sector data
into
the highest
512
bytes
of
the
standard
RAM
memory
and
transfers control
to
it.
Usually,
the
Tandy
600's
diskette
does
not include
any
booter
and
uncooperative
system
program.
The
ROM-BIOS
transfers control with
CLI
(disable
INT)
state.
Therefore, the
STI (enable
INT)
should
be
done
after
control
is
transferred.
166
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