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IBM 7090 User Manual

IBM 7090
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4.
O.
00 IBM 7606
MULTIPLEXOR
The
IBM 7607
Multiplexor
is
best
described
as
the
unit
of
the
7090
system
that
passes
all
data
to
or
from
core
storage.
These
data
may
be
CPU
instructions,
data
channel
commands,
data
to
be
processed
by
the
CPU,
data
that
has
been
processed
by
the
CPU,
or
input-output
words.
Data
that
go
to
core
storage
come
to
the
multiplexor
from
the
CPU
and
data
channels.
Multiplexing
is
the
forming
of
parallel
paths
from
a
serial
path
when
data
are
going
to
core
storage.
When
data
are
coming
from
core
storage,
multiplexing
is
the
forming
of
a
serial
path
from
parallel
paths.
In
addition
to
its
function
of
multiplexing,
the
multiplexor
contains
the
clock
for
the
CPU
and
data
channels,
and
a
matrix
for
zero
testing
data
coming
from
core
storage.
The
multiplexor
also
contains
look-ahead
circuits
that
are
used
in
conjunction
with
the
data
channel
operations.
The
CPU
clock
and
CPU
multiplexing
circuits
are
described
in
this
manual;
the
remainder
of
multiplexor
functions
are
described
in
Customer
Engineering
Manual
of
Instruction,
IBM 7607
Data
Channel,
Form
223-6898.
Two
of
the
four
standard
modular
system
(SMS)
sliding
gates
in
the
multiplexor
frame
are
reserved
for
special
features.
The
remaining
two
SMS
sliding
gates
house
the
multiplexor
circuitry.
Data
flow
from
core
storage
to
the
multiplexor
storage
bus,
then
to
either
the
CPU
or
anyone
of
the
data
channels.
See
Figure
4.0-1.
The
address
field
(21-35) of
the
data
coming
from
core
storage
also
flows
to
the
multiplexor
address
switches.
The
flow
through
the
multiplexor
address
switches
is
controlled
by
the
look-ahead
circuits
in
the
multiplexor.
Data
going
to
core
storage
flow
through
the
multiplexor
storage
bus
OR'ing.
This
bus
is
a
group
of OR
circuits
that
multiplex
data
going
to
core
storage.
It
is
completely
independent
of
the
multiplexor
storage
bus.
The
multiplexor
address
switches
receive
addresses
from
the
CPU,
data
channels,
and
the
multiplexor
storage
bus.
These
switches
multiplex
the
address
sent
to
core
storage
and
the
location
counter
switches
in
each
data
channel.
4.1.
00
MULTIPLEXOR
FUNCTIONAL
UNITS
The
multiplexor
contains
the
multiplexor
clock,
storage
bus,
storage
bus
OR
'ing,
and
the
address
switches.
4.1.
01
Multiplexor
Clock
The
multiplexor
clock
(Figure
4.
1-1)
supplies
timing
pulses
to
the
7090
system.
The
clock
consists
of
a
12-stage
ring.
The
clock
is
started
by
turning
on
the
zero
clock
trigger
with
a
start
clock
pulse.
The
AO(Dl)
clock
pulse
is
obtained
by
gating
the
last
half
of
the
zero
clock
trigger
pulse
with
the
negative
portion
of
the
even
ring
drive
pUlse.
The
rise
of
the
AO(Dl)
pulse
turns
on
one
clock
trigger.
The
Al(Dl)
pulse
is
obtained
38

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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