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IBM 7090 User Manual

IBM 7090
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The
"invert
SI"
has
no
effect
on
the
SI
position
if
there
is
no
bit
in
the
corresponding
position
of
the
storage
register.
With
a
bit
in
the
SR
and
the
invert
line
active,
the
information
in
the
SI
will
be
inverted.
7.1.
05
Shift
Counter
(Systems
03.04.14.1-03.04.19.1)
The
shift
counter
is
an
18-position
counter
of
triggers.
It
is
a
step-down
counter
when
used
for
shifting.
The
shift
counter
is
also
used
as
part
of
the
program
register
for
certain
instructions.
During
a
shifting
operation,
the
counter
will
be
stepped
every
clock
pulse
(Figure
3.1-7A).
Lines
controlling
the
shift
counter
are:
AS
to.SC
Step
SC
02.11.
78.1
02.11.
79.1
7.1.06
Program
Counter
(Systems
03. 05. 00.
1-03.
05. 07. 1)
The
program
counter
is
a
16-position
counter
of
triggers.
These
positions
are
labeled
2
through
17
(Figure
3.
1-7B).
Lines
controlling
the
program
counter
are:
ADV
PROG
CTR
PC
to
AS
02.11.
51.1
03.05.09.1
The
program
counter
is
a
count-up
counter,
and
can
sequentially
step
through
a
program.
7.1.
07
Accumulator
(Systems
02.03.00.1-02.03.37.1)
The
accumulator
is
a
38-position
register
of
shift
cells.
Some
trouble
may
result
from
the
"CP
set"
being
in
error.
This
is
true
for
all
registers
made
up
of
shift
cells.
Do
not
vary
the
"CP
set"
until
all
other
possibilities
have
been
checked.
Refer
to
Section
7
for
adjustment
of
the
"CP
set."
Lines
controlling
the
accumulator
are
shown
in
Figure
7 .
1-5.
Shift
Right
02.12.36.1
Shift
Left
02.12.35.1
SR
to
ACC
02.10.15.1
Adder
to
AC
02.12.32.1
Set
ACC
02.05.03.1
Hold
ACC
02.05.03.1
7.1.
08
Multiplier
Quotient
(Systems
02.04.00.1-02.04.35.1)
The
MQ
is
a
36-position
register
of
shift
cells.
The
MQ
is
used
on
multiply
and
divide
operations,
although
some
other
operations
may
use
it
(Figure
7.
1-4).
Lines
that
control
the
MQ
are:
SR
to
MQ
Shift
MQ
Left
Shift
MQ
Right
Set
MQ
Hold
MQ
02.12.40.1
02.12.44.1
02.12.45.1
J
02.05.04
and
102.05.05.1
168

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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