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IBM 7090 User Manual

IBM 7090
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Display
Effective
Address
(Figure
6.1-7)
The
display
effective
address
key
initiates
the
calculation
of
the
effective
address
of
the
instruction
in
the
storage
register.
The
actual
addres
s
from
the
storage
register
is
combined
with
the
two's
complement
of
the
specified
index
register
to
produce
the
effective
address.
The
calculated
address
is
then
placed
in
the
address
portion
of
the
storage
register.
Positions
1
through
20
of
the
storage
register
are
set
to
zero.
The
effective
address
may
be
calculatetl
only
once
because
the
positions
18,
19,
and
20
of
the
storage
register
have
been
set
to
zero,
an
indication
of
no
index
register.
Single Step
(Figure
6.1-8)
Pressing
the
single-step
key
results
in
executing
the
instruction
whose
address
is
in
the
instruction
counter
prior
to
key
depression.
The
instruction
counter
will
be
advanced,
or
altered,
under
control
of
the
instruction
executed,
once
for
each
time
the
key
is
pressed.
If
an
I-a
operation
is
executed,
the
machine
will
continue
to
execute
instruc-
tions
at
high
speed
until
the
end
of
the
I-a
operation.
If
the
continuous
enter
instruction
switch
is
on,
the
single-step
key
is
pressed,
and
the
7090
is
in
manual
status,
the
in-
struction
set
in
the
OP
keys
will
be
executed
once.
The
single-step
key
is
effective
only
if
the
system
is
in
manual
status,
and
not
in
program
stop
status.
Multiple
Step
(Figure
6.
1-~)
This
key
is
effective
only
in
manual
status
with
the
program
stop
trigger
on.
The
multiple-step
key
causes
the
repetition
of
single-step
operations.
The
rate
of
operation
is
under
control
of
a
toggle
switch
located
on
the
customer
engineer
test
panel.
The
operator
has
the
choice
of low
speed
with
a
delay
of
104
milliseconds
between
each
in-
struction,
or
high
speed
with
a
delay
of
24
milliseconds
between
each
instruction.
The
program
will
continue
to
run
as
long
as
the
multiple
step
key
is
pressed,
or
until
a
pro-
gram
halt
is
decoded.
Enter
MQ
Key
The
enter
MQ
key
provides
a
means
for
loading
the
MQ
register
from
the
operator's
entry
keys.
The
information
may
then
be
loaded
into
storage
by
placing
the
instruction
STQ
along
with
the
desired
address
in
the
entry
keys
and
depressing
the
enter
instruc-
tion
key.
The
enter
MQ
key
is
effective
only
when
in
manual
status.
See
Figure
6.1-10.
Enter
Instruction
(Figure
6.1-11)
With
the
machine
in
manual
status,
the
enter
instruction
key
executes
completely
and
correctly
any
legitimate
instruction
entered
in
the
operator's
panel
entry
keys.
The
contents
of
the
instruction
counter
remain
unchanged
when
an
instruction
is
executed
(except
for
a
transfer
or
a
skip
type
of
instruction).
The
key
is
effective
only
in
manual
status.
Load
Cards
(Figure
6. 1-12)
The
load
cards
key
causes
a
reset
of
the
instruction
counter,
address
register,
pro-
gram
stop
trigger,
simulate,
and
all
channels
not
in
manual
status.
Pressing
the
load
cards
key
then
causes
a
select
of
the
card
reader
on
channel
A,
reads
the
first
three
words,
and
proceeds
to
storage
locations
zero
for
the
next
command
word.
This
is
accomplished
by
bringing
up
"load
ctrl,"
which
fires
a
1-usec
Single-shot.
The
auto
load
trigger
goes
on
in
the
CPU,
selecting
the
card
reader
on
channel
A.
The
word
counter
is
set
to
three,
and
indicator
S
is
turned
on
in
channel.
Three
words
from
the
first
155

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IBM 7090 Specifications

General IconGeneral
CategoryMainframe Computer
Introduced1959
Transistor-basedYes
Word Length36 bits
Add Time4.8 microseconds
MemoryCore memory
Memory (words)32, 768 words