IBM 7090 User Manual

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Entry

Keys

There

are

36

entry

keys

on

the

operator's

panel:

S,

1-35.

Depressing

a

key

sets

a

1

in

that

position;

leaving

a

key

normal

sets

a 0

in

that

position.

Information

set

in

the

entry

keys

may

be

entered

into

storage,

executed,

or

used

for

a

storage

inquiry

address.

The

entry

keys

may

all

be

reset

to

0

by

depressing

the

reset

key

to

the

right

of

position

35.

6. 1.

03

Manual

Control

Keys

When

any

manual

control

key

is

pressed,

a

series

of

single-shots

and

triggers

are

set.

Separating

the

key

from

the

usable

signal

prevents

false

indications

from

noise

generated

by

the

key

(Figure

6.1-2).

Three

single-shots

are

fired

in

sequence:

a

1-usec,

a

20-ms

and

a

350-usec.

The

350-usec

single-shot

is

taken

through

a

delay

network

to

develop

a

200-ns

pulse

that

turns

on

the

manual

control

trigger.

By

this

time,

the

switch

has

settled

down

and

the

trigger

to

perform

the

desired

operation

turns

on,

resetting

the

manual

control

trigger.

Start

Key

(Figure

6.1-3)

If

the

CPU

is

in

automatic

and

ready

status,

pressing

the

start

key

initiates

machine

operation

by

turning

off

the

master

stop

trigger

and

the

program

stop

trigger.

The

master

stop

trigger

off

conditions

"not

B

cycle

interrupt,"

allowing

the

computer

to

proceed.

If

the

system

is

in

manual

status,

pressing

the

start

key

turns

off

the

program

stop

trigger.

Clear

Key

(Figure

6.1-4)

The

clear

key

is

only

operative

if

the

computer

is

in

automatic

status.

Pressing

the

clear

key:

1.

Fires

a

1-usec

single-shot

to

reset

the

clock

and

all

channel

registers

of

channels

that

are

not

in

manual

status.

2.

Resets

CPU

interlocks

and

registers.

3.

Conditions

circuits

which

allow

zeros

to

be

written

into

all

storage

locations.

The

program

counter

controls

the

stepping

through

memory,

with

position

2

of

the

PC

indicating

when

all

addresses

have

been

zeroed.

The

turn-on

of

PC2

trigger

will

turn

on

the

master

stop

trigger

at

E10.

Display

Storage

(Figure

6.

1-5)

pressing

the

display

storage

key

causes

the

address

portion

of

the

operator's

panel

keys

to

be

sensed,

to

determine

the

address

in

storage

to

be

displayed.

All

36-bit

posi-

tions

of

the

address

will

be

displayed

in

the

storage

register.

This

is

accomplished

by:

(1)

turning

off

the

master

stop

trigger,

(2)

bringing

the

operator's

panel

keys

to

the

storage

register

in

I

time,

and

(3)

suppressing

"storage

bus

to

storage

register."

The

address

portion

of

the

SR

is

routed

through

the

adders

and

address

switches,

to

the

address

register.

During

E

time,

the

SB

is

gated

to

the

SR,

which

contains

the

36

bits

of

the

desired

address.

If

a

tag

or

indirect

addressing

is

specified

in

the

operator's

keys,

the

contents

of

the

effective

address

or

the

I-A

address

will

be

displayed.

Display

Indicators

The

display

indicators

key

gates

the

true

value

of

the

sense

indicators

to

the

stor-

age

for

display

(Figure

6.1-6).

151

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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