IBM 7074, 7000, 7080, 7070, 7090 General Information Manual

General

Information

Manual·

IBM
IBM

1301

7000

Disk

Series

Storage

Data

with
Processing Systems

Preface

This

manual

tory information on

Storage
Since

the
length
length
addressing schemes,
out,

and

tempt

to give specific details for these areas; the varia­tions

are
bulletin for
systems
the

7631 File Control has
tions section of this manual.
reader
the

major

is

intended

with

IBM

7000 series

7000 systems include

systems

system

(7070,7074,7090)
(7080),

data

transmission. This

described in a

each

system. Information common to 7000

in

the operation of

to provide general introduc-

the

use of

the

IBM

Data

Processing Systems.

both

and

a variable

minor variations occur

track

capacity, core storage lay-

manual

separate

IBM

1301 Disk Storage

the

1301 Disk Storage

been

included

It

is assumed

has a practical working knowledge of one of

IBM

data

processing systems.

the

in

fixed

does

the

1301 Disk

word
word

in

the

not

at-

and

Opera-

that

the

MAJOR

REVISION

This edition,
and

IBM

N22-0035, N22-0039,

Address comments concerning this

IBM Corporation
Customer Manuals, Dept. 298
P.O.

Box

Poughkeepsie,

© 1961, 1962

(October, 1962)

Form

D22-6576-3, obsoletes Form D22-6576-2,

Technical Newsletters, Forms N22-0029, N22-0031,

and

N22-0061.

390

N.Y.

by

International Business Machines Corporation

manual

to:

Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Magnetic Disk Recording. . . . . . . . . . . . . . . . . . . . . . . . . . .

Functions

Operations

Control
Sense
Write
Read
Checking

Shared System Operation. . . . . . . . . . . . . . . . . . . . . . . . . . .

Instruction Times
Access Motion

.........................................

.....................................

...........................................

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.............................................

..........................................

...................................

Time.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Control Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Power-On Switches

and

Lights. . . . . . . . . . . . . . . . . . . . . .

Error Recovery Procedures. . . . . . . . . . . . . . . . . . . . . . .

..

..

" 10

10
12
13
15
16

..

17
18

..

18

..

20

..

20

..

21

5

5
9

IBM

1301 Disk Storage

IBM

1301

Disk

Storage

High-speed magnetic disk storage provides large ex­ternal storage capacity to supplement internal core

The

IBM

storage of a computer system.
Storage

and

its associated

IBM

7631 File Control pro-

1301 Disk

vide very large storage capacity, fast access time to

the

disks,

and

data recorded on

the ability to handle

fixed or variable length records.

Significant advantages are:

1.

Lower cost

2.

Entire program libraries contained in readily

per

character of storage.

accessible form.

3.

Access to any program or active file

in

50-180

milliseconds.

4.

Table storage.

5.

Simplification of program scheduling.

6.

Ability to

dump

and

recover files into or from

core storage rapidly.

7.

Customer control of addressing schemes

and

record length format.

8.

Improved checking techniques - more reliable
data

recording.

The

1301

Disk Storage

are available for use with

and

1410

7090,

The

1301

Data

Disk Storage

and

the

7631 File Control

the

IBM

7070, 7074, 7080,

Processing Systems.

is

available in two models:

:Model 1 - single module, providing capacity for

28,000,000 (7080)

characters-or,

using

packed format, 43,300,000 digits.

Model 2 - two modules, providing capacity for

56,000,000 (7080) characters - or, using
packed format, 86,600,000 digits.

The

7631 File Control

1-

Model

for use with a 1410 system

Model 2 - for use

is

available in four models:

with

a 7000 system (7070,

7074,7080, 7090)

Model 3 - for shared use with a 7000 system

and

a 1410 system

Model 4 - for shared use with two 7000 systems

Index or Reference Point

~

250

Data Tracks

Within This Area

Figure

1.

Magnetically

Data

are stored as magnetized spots in concentric

tracks on each surface of

Coated

Disk

the

disk

(Figure

1).

There
are 250 tracks for the storing of data on each surface.
The

tracks are accessible for reading and writing

positioning

the

read-write heads between

the

by

spinning

disks.

The read-write heads are mounted. on an access
mechanism which has 24 arms, arranged like
a comb
the disks.

(Figure

(No

2),

that

move horizontally between

vertical motion

is

involved.)
write heads are mounted on each arm. One of
heads services
while

the

lower disk. Thus, it is possible to

other

the

bottom surface of the

head

services

the

top

read

teeth

Two

upper

surface of

or write on

on

read-

the

disk

the

either side of a disk.

Head

services

Head servi
bottom
of

ces

surface

upper disk

Magnetic Disk Recording

The

magnetic disk is a thin metal disk coated on
sides with magnetic recording material. Twenty-five
disks are mounted on a vertical shaft; they are slightly
separated from each other to provide space for
movement of read-write assemblies.
spinning
per

the

minute.

disks

at

a maximum of 1790 revolutions

The

shaft revolves,

both

the

Figure

2.

Head

Arrangement

Introduction 5

The

magnetic disk
tively.
track, the old
corded.
desired;
until

provides external storage capacity
ternal core storage of a computer. Disk storage has a
major advantage, however, in
tained in
random
is, faster access to

the track
records
be
data
arrangement
ments. Addresses must
track
also, space
separate address
for

fining
areas. for
monitors 40 associated
can
data
of

25 magnetic disks
Of
store data; of
alternate surfaces, one is a format surface, one is a
clock surface
The
contain 250 concentric tracks
reading

Cylinder Concept

Since
aligned one above
the tracks

(Figure
in
available without
electronic
for one access mechanism setting, as
characters (7080)

bottom to

Each

time

is

The

recorded

data

remain

written

Disk storage, like trays of cards or magnetic tape,

Although

arranged

can

and

the

A format track is used to provide a means of de-

be

track format as often as

the

A disk storage

the

data

anyone

The

over.

the

1301 are program-addressable, providing

access to

the

is

fixed,

and

the

to suit

be

stored on

within

the

must

records.

and

monitoring

the

data

written

user.

25 disks, 20 disks

the

(Figure

storage surfaces

and

writing.

the

heads

can

4).

Thus,

of

the

head

tracks

the

top

data

surface can

new

information

erased as

any

any

total

the

number

the

individual records to

be

and

tracks.

and

module

and

other

and

the

be

considered as a cylinder of tracks
with

250 cylinders, 40 tracks of

any

switching is necessary.

are

are

numbered

of

the

the

new

data

may

recorded

record or group of records

record).
number
arrangement

needs of

the

provided

record areas, as well as

the

data

rewritten to describe

its associated access mechanism.

3).

disk tracks

other,

the

available.

cylinder (corresponding

in

of character positions of

of characters

the

the

track in any convenient

limitations of track require-

be

provided to identify

in

address, record,

In

the

1301, one format track

tracks.

required

is

comprised of

(40

surfaces)

ten

surfaces, six

The

other

and

the format surface

that

the

access mechanism

further

sequentially, from

be

used repeti-

is

stored on a

information

be

read

as often as

the

tracks of a disk

to

supplement in-

that

all records con-

as to

the

number

per

record can

using system. Thus,

the

computer;

the

form of gaps to

The

format

the

to

suit

the

are
are

two

are

are

accessible for

are

mechanically

vertical alignment of

access motion; only

For

many

as 112,000

is

re-

(that

the

the

areas

and

gap

track

desired

the

needs

stack of

used
used as

not

used.

each

placed

data

are

example,

the

to

the

of

to

Figure

3. Disk Surfaces

40 heads, 00 to

(000) to
large storage areas for reference tables,
be

conveniently stored in a cylinder of tracks
number
duce access time to a minimum.

optional feature, the cylinder mode of operation,
read
tracks in one operation.

Data

The
track.
track to a specific overall recording capacity. All
tracks
recording area cannot
a
provide a means of identifying
system, or a home address (

One

Cylinders

Figure

of adjacent cylinders. This technique will re-

The

cylinder

or write a cylinder,

Tracks

basic fixed recording area of

The

are

number

of

250

4. Cylinder

39),

starting

the

innermost cylinder (249).

arrangement

physical make-up of

equal

in overall storage capacity.

of character positions must

Concept

at

the

outermost cylinder

of tracks also permits

(or

part

the

the

be

used to store data, however;

the

track

HA).

To

Thus

the

data

or

of a cylinder) of

1301 is
track limits

be

provide

--1-

__

the

The

set aside

to

the

random

20 Data

Disks

(40 Surfaces)

1

__

entire

using

-

with

can

in a

the

to

data

the

data

to

6

access to any record on the track, additional character
positions must
a record address
are required for gaps

be

used for each record on

(RA).

Additional character positions

(G)

to separate addresses

the

track, or

and

records. Since the tracks are circular, an index point

I)

must

be

(

used to indicate

of the track. Therefore, each of the 10,000

the

beginning or

data

the

tracks

end

must have an index point, one home address, a record

the

track,

and
the rec-

by

the

the

and

file

address for each record stored on
necessary gaps to separate
ords (Figure

INDEX

POINT

The

index point of the track is the reference point of
the track,
the end of the track.

that

5).

is,

it

indicates

The

the

address

both

index point

and

the beginning

is

used
control in conjunction with its various modes of opera­tion.

HOME

ADDRESS

There is one home address for each of

tracks.

The

(HA)

home address follows

the

index point

the

10,000

and

consists of two parts called home address one (HAl)
and

home address two (HA2).

HAl:

This portion of the home address is the track

number.

the customer.

(

0000-9999) indicating the physical location of the
track within
sequentially, beginning
most cylinder, track number
through
ing

the

HAl

is prerecorded; it cannot be written
The

track number

the

module.

at

the

cylinder to track number 0039, represent-

40

data

tracks of the outermost cylinder. The

is

a four-digit number

The

tracks are numbered

the lowest track of

0000,

and

continuing

the

by

outer-

up

numbers continue with the lowest track of the ad­jacent cylinder, track number
track number

0079. Continuing through each of
cylinders in a like manner,
is

the top track of

the
method of numbering, adjacent tracks on
disk always differ
determining
cylinder
ber

and

product of

the

by

the

the

cylinder number, the track

the

by

40.

track number for any track within any

simple formula: Given the

cylinder number
number. For example, for cylinder
head number

241 X 40

20

the track number is:

= 9640; 9640 +

0040,

up

the

cylinder to

the

last track number, 9999,

innermost cylinder.

With

the

This provides a means of

head

number

and

40, plus the

20

= 9660.

number

241

the

this

same

num-

is the

head

and

Also, with the track number known,

and

head

number
dividing the track number

number can

by

cylinder number; the remainder

be

40; the quotient is

is

For example, given the track number,

40

0590 +

Thus, the cylinder number
is

30.

HA2:

The

= 014 with a remainder of 30.

is

014 and

second portion of the home address is

called the home address identifier. This portion of

address further identifies the track to

HA2

is

written

characters

that

by

the user

can

and

consists of two or more

be

numeric, alphabetic, or special

the

determined

the

head

0590,

the

head

the

using system.

cylinder

by

the

number.

number

the

characters, depending upon the requirements of the
using system. Two characters are required for

HA2;

even though only two characters are compared during

address verification operations, additional characters
can

be

used as a convenience for fixed word length

systems.

HA2

can

be

written to serve any convenient purpose.

It

can

be

used as a coded

be

used to identify or tag a category of records, such

file

protect device or

it

can

as receipts, withdrawals, payments, inventory, etc.

HAl

and

HA2

can

be

treated as one six-position ad-

dress

that

corresponds to a six-position key of record,

part

number, policy number, account number, etc.

RECORD ADDRESS

The

record address consists of six or more characters

that

can

be

numeric, alphabetic, or special characters.

It

is

used to identify the individual record on
to the using system. A record address is assigned
written
scheme;
address of
dress
tional order.
and

(single record) order, need not

ters
tions) can
the 7080

by

the

user to

it

need not have any relationship to the home

the

track where

is

transmitted to the

The

the record address, used

The

record address normally consists of six charac-

and

even though the first four (high-order posi-

be

alphabetic or special characters

and

7090, only

fit

any convenient addressing

it

is

written, since an ad-

file

control for each func-

home address, used for seek orders,-

in

the prepare to verify

be

related in any way.

the

numeric

the

bit

positions of

track

and

with

these characters are compared during address verifica­tion operations. All bits of the' fifth
ters are compared during address verification.

and

sixth charac-

The

Index
Point

~

-{

Figure

HA 1

~

5. Track Layout

GAP

HA 2

GAP

Record

Address 1

GAP

Record t

Record

Address 2 Record 2

GAP

GAP

Introduction 7