7.
Determine
if
Internal
HP-IB
is
Present:
Register A6 is set
to
the
address of
the
next
step. Channel zero
of
the
DMA
card
is
disarmed if
the
DMA
card
is present. An internal
HP-IB
card
is
present if register
three
is
set
up
such
that
bit 7 =
1,
bit
6 = 0
and
bit
0 = 0,
and
if
bits
7
and
6 are unaffected
by writing,
and
if
bits
7,
6,
and
0 are unaffected by bus precharging.
8.
Determine
Which, if any,
Alpha
video
card
is
Present:
Register A6
is
set
to
the
location
of
the
top
RAM
test
routine. Note
that
only video
assemblies with a
CRT
ID registers are
supported.
9.
Initialize
and
Blank
Alpha
Display Controller, if Present:
If
an
HP
98546A
card
set is present,
then
it will
be
initialized
and
blanked.
10.
Top RAM Test:
Register A6
is
set
to
the
location of
the
fatal
error
handler
routine. A memory
test
is
executed on
just
enough
RAM
to
allow
the
rest
of
the
Boot
ROM
code
to
operate.
(A
"fatal error" will occur when
there
is
not
enough RAM.)
If
there
is
a memory failure,
8416
will
be
displayed on LEDs.
If
nlemory
is
missing,
4416
will
be
displayed on LEDs.
If
an
alpha
display controller
is
present,
the
Boot
ROM will also write one of these messages:
RAM
FAILED
ABOVE
FFCOOO
RAM
GONE
ABOVE
FFCOOO
for menlory failure
and
mernory missing, respectively. These messages will
not
be
displayed
on a
monitor
through
a
bit-mapped
video
board.
NOTE
If
high RAM fails
or
is
missing,
then
the
LEDs
and
beeper
will give
the
only notification on a system with a
bit-mapped
video
board
or
remote
console.
11.
Set Up
Data
Structures:
a.
The
two global variables SYSFLAG
and
SYSFLAG2 are set up.
b.
ATTENDED
is
set
to
false.
ATTENDED
is
a
Boot
supervisor flag which indicates
whether
or
not
the
keyboard has been accessed.
c.
The
test
list is set
up
in
temporary
RAM.
d.
The
Boot list
and
device driver list are set up.
NOTE
The
remaining
steps
depend
upon
a working RAM stack. As in
the
previous steps,
the
LEDs are set
to
a new value before each step.
Boot
Rom Functions
85
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