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IBM 7090 User Manual

IBM 7090
190 pages
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The
recognition
circuits
are
shown on
Systems
2.10.50.1.
To
set
position
14
of
the
decrement,
the
floating-point
divide
occurred
trigger
is
used.
To
set
position
15,
the
floating-point
overflow
trigger
is
turned
on
by
a
bit
in
(P)
only.
To
set
position
16,
a
bit
in
ACC (P)
is
all
that
is
required.
To
set
position
17 t
the
MQ
overflow
trigger
is
turned
on
by
an
adder
(P)
output
while
the
MQ
characteristic
is
being
computed.
The
controls
for
floating-point
trap
are
shown
on
Systems
2.10.51.1.
An
overflow
or
underflow
causes
the
floating-point
trap
trigger
to
be
turned
on.
This
trigger
initiates
a
pseudo
STR
instruction
by
blocking
the
instruction
following
the
floating-point
instruc-
tion
during
which
the
condition
occurred
and
setting
IR
sign
(-)
and
a one
in
IR (9).
Address
0000
is
set
into
the
address
register,
store
decrement
and
store
address
con-
troIs
are
activated,
and
an
E
cycle
is
initiated.
The
program
counter
and
the
four
spill
code
lines
are
routed
to
the
storage
bus
and
stored
in
location
0000.
The
address
regis-
ter
is
then
set
to
0010
8
to
locate
the
next
instruction
to
be
executed.
143

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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