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IBM 7090 User Manual

IBM 7090
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Enter
Keys
ENK
+0760
...
0004 (I, L)
Figure
5.3-8
The
word
represented
in
console
keys
(S,
1-35)
replaces
the
contents
of
the
MQ.
This
is
a
primary
operation
76
instruction.
The
word
in
the
keys
is
put
into
the
SR
and
the
output
of
the
SR
is
gated
into
the
MQ.
5.3.02
Shifting
Instructions
Shift
instructions
are
used
to
align
words,
or
for
fast
multiplication
or
division
by
a
power
of 2.
Shifting
moves
the
bits
of
the
AC
or
MQ,
or
both,
to
the
right
or
left
within
the
registers.
Bits
shifted
out
of
the
end
of a
register
are
lost
and
bits
shifted
away
from
either
end
of
a
register
are
replaced
by
zeros.
Because
the
shift
counter
receives
only
the
last
eight
positions
of
the
instruction
address,
the
maximum
number
of
shifts
possible
is
25510 (11 111
1112).
The
number
of
shifts
to
be
taken
is
indicated
by
the
address
portion
of
the
shift
in-
struction.
This
address
is
gated
to
the
shift
counter
at
I11(D1).
Shifting
starts
at
the
next
L1
time
and
continues
to
shift
at
the
rate
of
one
position
of
shift
for
each
clock
pulse
until
the
shift
counter
has
been
reduced
to
zero.
The
cyclic
makeup
of
a
shifting
instruction
is
an
I
time
followed
with
as
many
L
times
as
required
to
complete
the
shifts
designated
by
the
address
portion
of
the
instruction.
Eleven
shifts
may
be
completed
during
the
first
L
time,
and
twelve
shifts
may
be
com-
pleted
during
all
succeeding
L
times.
The
"end
operation"
condition
is
Signaled
by
having
the
shift
counter
at
seven
or
less
at
any
L10
time
of a
shift
instruction.
This
means
that
up
to
five
shifts
may
be
made
in
the
1
time
of
the
following
instruction.
Shifting
to
the
left
is
the
same
as
multiplying
by
a
power
of 2;
shifting
to
the
right
reduces
or
divides
by
a
power
of
2.
The
number
of
shifts
is
equal
to
the
exponent.
Accumulator
Left
Shift
ALS
+0767 (I, L
.••
)
Figure
5.3-9
This
instruction
causes
the
contents
of
the
AC (Q-35)*
to
be
shifted
left
a
number
of
places
equal
to
the
eight
low
order
positions
of
the
address.
Zeros
replace
any
bits
shifted
away
from
position
(35).
Bits
shifted
past
Q
are
lost.
A
"1"
shifted
into
the
P
position
turns
on
the
AC
overflow
indicator.
Long
Left
Shift
LLS
+0763
(I,
L
...
)
Figure
5.3-10
For
this
instruction
the
contents
of
the
MQ
and
A C
(except
the
sign
positions)
are
shifted
left
the
number
of
places
deSignated
by
the
eight
low
order
positions
of
the
ad-
dress.
The
MQ
(1)
position
is
shifted
to
the
AC
(35)
position.
The
AC
sign
is
set
to
agree
with
the
MQ
sign.
Bits
shifted
past
Q
are
lost
and
bits
shifted
away
from
MQ(35)
are
replaced
by
zeros.
Bits
shifted
into
P
cause
the
AC
overflow
indicator
to
be
turned
on.
Logical
Left
Shift
LGL
-0763
(I, L
••.
)
Figure
5.3-10
This
instruction
shifts
the
contents
of
AC(Q-35)
and
MQ(S-35)
left
the
number
of
places
designated
by
the
address.
Bits
shifted
from
MQ(l)
enter
MQ(S) ,
and
from
MQ
(S)
enter
AC(35).
Bits
shifted
into
AC(P)
cause
the
AC
overflow
indicator
to
be
turned
on.
Bits
shifted
past
AC(Q)
are
lost
and
bits
shifted
away
from
MQ(35)
are
replaced
by
zeros.
The
operation
of
LGL
is
similar
to
LLS
except
for
handling
of
the
MQ
sign.
*
This
text
section
uses
(Q
- 35)
to
represent
(Q,
P, 1 -
35).
53

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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