IBM 7090 User Manual

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Divide

Check

The

divide

check

lamp

is

turned

on

in

fixed

point

division

if

the

dividend

accumu-

lator

(AC)

is

greater

than

or

equal

to

the

divisor

(storage

register).

In

floating-

point

divide

the

lamp

is

on

if

the

magnitude

of

the

fraction

of

the

dividend

is

greater

than

or

equal

to

twice

the

magnitude

of

the

fraction

of

the

divisor.

The

indicator

may

be

tested

by

the

DCT

instruction

.•

Channel

Select

(A-H)

The

channel

select

(A-H)

lamps,

one

for

each

channel,

are

on

according

to

the

data

channel

that

is

in

operation.

They

are

off

when

the

channel

is

not

in

operation.

Command

Word

Trap

(Channels

A-H)

These

lamps

are

turned

on

according

to

the

corresponding

channel

that

is

enabled

to

trap

on

command

word

or

end

of

file.

The

lamp

for

a

particular

channel

is

turned

off when the

channel

is

disabled.

Tape

Check

Trap

(Channels

A-H)

These

lamps

are

on

according

to

the

corresponding

channel

that

is

enabled

to

trap

on a

tape

check.

The

lamp

for

a

particular

channel

is

off

when

the

channel

is

disabled.

Channel

Tape

Check

These

lamps,

one

for

each

channel,

are

on

if

any

error

is

detected

while

writing

or

reading.

The

lights

may

be

turned

off

by

the

execution

of

a

Transfer

on

Redundancy

Check

instruction.

Trap

Control

This

lamp

is

on when

the

channel

is

not

executing

a

channel

trap.

It

is

off

when

any

channel

enters

a

trap

condition.

While

the

light

is

off, no

channel

traps

may

be

executed.

Channel

traps

may

be

executed

only

when

the

light

is

on

at

the

same

time

as

any

of

the

enabled

lamps.

Program

Stop (Red)

The

program

stop

lamp

is

turned

on

whenever

the

computer

executes

a

halt

instruc-

tion

and

no

data

channels

are

in

operation

(DVH

or

VDH

excepted).

1-0

Check

(White)

The

1-0

check

lamp

may

be

turned

on

by

any

of

the

following

conditions:

1.

If

aRCH

or

LCH

is

decoded

and

the

specified

data

channel

has

not

been

selected.

2. If,

when

writing,

a

data

channel

data

register

has

not

been

loaded

with

a

word

from

storage

by

the

time

its

contents

are

to

be

sent

to

the

output

unit.

147

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IBM 7090 Specifications

General

Category	Mainframe Computer
Introduced	1959
Transistor-based	Yes
Word Length	36 bits
Add Time	4.8 microseconds
Memory	Core memory
Memory (words)	32, 768 words