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IBM 7090 User Manual

IBM 7090
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opposite
end
of
the
register.
Positions(8-5)*
of
the
table
word
are
entered
into
the
six
cleared
positions,
and
the
next
group
of
six
bits
is
in
position
to
add
to
the
starting
lo-
cation
of
the
next
table.
The
process
continues
until
up
to
six
references
have
been
made.
The
controlling
register
is
gradually
replaced
by
six-bit
entries
from
the
stor-
age
tables.
When
the
number
of
references
specified
by
the
count
has
been
made,
the
conversion
is
complete.
The
tag
of
the
instruction
has
a
unique
function
for
the
convert
instructions.
Positions
(18)
and
(19)
are
not
used,
but
a
bit
in
(20)
will
cause
the
storage
table
starting
location
contained
in
the
last
reference
word
to
be
stored
in
index
register
A.
Convert
by
Replacement
from
Accumulator
CVR +0114 (Min
I,
L)
Figure
5.3.
71
(Max
I,
L,
6E)
This
instruction
treats
the
contents
of
the
AC(P,
1-35)
as
six
6-bit
representations.
The
instruction
replaces
a
number
of
these
representations,
equal
to
the
count
of
the
instruction,
with
the
contents
of
positions
(S-5)
of
a
like
number
of
words
from
storage.
These
words
are
found
by
adding
AC(30-35)
(the
first
six-bit
group)
to
SR(21-35)
(initially
the
instruction
address)
and
directing
storage
to
this
modified
address.
The
word
thus
found
is
brought
to
the
SRi
the
AC
is
shifted
right
six
places;
SR(S-5)
re-
places
AC(P,
1-5).
SR(21-35)
adds
to
the
next
six-bit
group
in
AC(30-35)
to
locate
the
next
word
in
storage.
The
process
is
then
repeated.
Mter
the
required
number
of
replacements,
the
address
portion
of
the
last
storage
word
can
be
stored
in
index
register
A
by
including
a
"tag"
bit
in
position
(20)
of
the
instruction.
The
following
illustrates
the
use
and
operation
of
CVR:
Direct
Addition
of
BCD
Numbers:
A
134589
+ B
+
691593
Table
required
in
storage
for
this
example:
Storage
Contents
Location
(S-5)
(21-35)
1000
0
1000
1001
1
1000
1002
2
1000
1003
3 1000
1004
4 1000
1005
5 1000
1006
6
1000
1007
7 1000
1008
8
1000
1009
9
1000
Instructions
required
for
operation:
CAL
A
(First
BCD
word)
ADD B
(Second
BCD
word)
C
826182
Storage
Location
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
CVR
6,
0,
1000
(Convert
sum
to
BCD
word)
*
This
text
section
uses
(S-5)
to
represent
(S,
1-5).
133
Contents
(8-5)
(21-35)
0
1001
1 1001
2
1001
3
1001
4
1001
5
1001
6
1001
7
1001
8
1001
9
1001

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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