Singer 40 User manual

REFERENCE MANUAL
MODELS 40 AND 42 DISC DRIVES
Copyright © 1972, The Singer Company
All rights reserved throughout the world.
Publication No. 40-298
January 1972
Re-order No. INT 10-211
R1
SINGER
BUSINESS MACHINES

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Page
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1-1 thru 1-3
2-1 thru 2-2
3-1 thru 3-2
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5-1
6-1
7-1 thru 7-3
8-1 thru 8-4
9-1
LIST OF EFFECTIVE PAGES
Effective Date
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Models 40 and 42 Reference Manual i

CONTENTS
Page
INTRODUCTION · · · · · 0-1
1 GENERAL DESCRIPTION
· · · · · · · · ·
1-1
2
OPERATOR CONTROL PANEL
· · ·
2-1
3 INSTRUCTION
FORMAT.
3-1
Read and Write Instructions
· · · · · .
3-1
Six-Character Disc Address
· · · · · ·
3-1
4
WroTE OPERATIONS . . · · · · · 4-1
5 READ OPERATIONS . . . · · · · · · · · · 5-1
6
MULTI-PARTITION CONSIDERATIONS .
6-1
7 TIMING CONSIDERATIONS • · · 7-1
8
OPERATING INSTRUCTIONS · · · . · ·
8-1
9 CONDITION CODE SUMMARY · · · · · · · . . · · . 9-1
ILLUSTRA TIONS
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Figure 1-1.
Figure 2-1.
Figure 3-1.
Figure 7-1.
Figure 8-1.
Figure 8-2.
Figure 8-3.
Model 40 Disc Drive .
Operator Control Panel .
Six-Character Disc Address
Disc Sector Layout . • • • . • . • •
Top View of a Model 41B Disc Pack in Its Carrying Case .
Top View of a Model 41A Disc Pack in Its Carrying Case.
Bottom View of a Model 41, 41A, or 41B Disc Pack in
Its Carrying Case .
1-1
2-1
3-2
7-2
8-1
8-2
8-3
Models 40 and 42 Reference Manual iii

Contents
TABLES
Table 1-1.
Table 2-1.
Table 7-1.
Table 7-2.
Table 9-1.
Specifications .
Operator Control Panel.
Timings.
Overlap Timings .
Condition Code Summary .
iv Models 40 to 42 Reference Manual
1-3
2-2
7-1
7-3
9-1
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INTRODUCTION
This manual is intended for those who are interested in the operating and pro-
gramming characteristics of the Models 40 and 42 Disc Drives. Included in
the manual are a general description of the Models 40 and 42; a table of speci-
fications; a description of the operator control panel; a thorough discussion of
read and write operations; discussions of multi-partition and timing consider-
ations; instructions on how to mount and remove disc packs; plus a summary
of all Condition Codes associated with the Models 40 and 42.
Detailed operating instructions may be found in the Model 40 Disc Drive
Operator Instructions, Publication No. 40-023, and the Model 42 Disc Drive
Operator Instructions, Publication No. 40-332.
Models 40 and 42 Reference Manual 0-1

1 GENERAL DESCRIPTION
The Models 40 and 42 Disc Drives are high speed, random access storage
devices designed as peripheral units for the System Ten* computer. Up to ten
disc drives may be attached to the central processor through the File Access
Channel (F AC). A Disc Controller, consisting of printed circuit cards con-
tained in the central processor, acts as intermediary between the disc drives
and the FAC. A particular installation may include both models in any combi-
nation. In external appearance, the two models are identical (see Figure 1-1);
what differentiates them is the type of disc pack used. Both models use
removable disc packs.
The Model 40 uses a disc pack consisting of six magnetic oxide coated discs
joined to one another on a common vertical axis. The discs are approximately
14 inches in diameter and there is approximately .4 inches between successive
discs. The disc pack (Model 41 Disc Pack) has ten recording surfaces. The
top surface of the top disc and the bottom surface of the bottom disc are not
used for recording data.
Figure 1-1. Model 40 Disc Drive
*A trademark of The Singer Company
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Models 40 and 42 Reference Manual 1-1

General Description
The Model 42 uses a pair of disc packs, one mounted on top of the other. Both
packs must be mounted for the disc drive to be operable. The bottom pack
(Model 41A Disc Pack) is referred to as the resident pack and the top pack
(Model 41B Disc Pack) is referred to as the removable pack. Regardless of the
terminology, both packs can be removed from the disc drive by the operator.
When both packs are mounted, they rotate together as though they were one pack.
It is anticipated that the resident pack will remain mounted for extended periods
of time with the removable pack being changed from run to run, day to day, etc.,
as dictated by the requirements of each installation. The resident pack and the
removable pack each consist of three magnetic oxide coated discs joined to one
another on a common vertical axis. The discs are approximately 14 inches in
diameter and there is approximately 0.4 inch between successive discs. Each
pack has four recording surfaces. The top surface of the top disc of each pack
and the bottom surface of the bottom disc of each pack are not used for record-
ing data.
On all three disc packs (Models 41, 41A, and 41B) each recording surface con-
tains 200 concentric tracks and each track is divided into 50 equal parts called
sectors. Each sector contains 100 characters. A write or read operation
always writes on or reads from a single sector.
The Model 41 Disc Pack has a maximum data storage capacity of 10 million
characters. The Models 41A and 41B Disc Packs each have a maximum data
storage capacity of 4 million characters.
The read/write head mechanism of the Model 40 Disc Drive has five arms, one
for each interdisc gap. Each arm has 'two heads: one for the surface above the
arm and the other for the surface below the arm. All five arms move together.
The read/write head mechanism of the Model 42 Disc Drive has four arms. The
mechanism is identical in appearance to the read/write head mechanism of the
Model 40 Disc Drive except that the middle of the five arms is missing.
Like all peripheral devices for the System Ten computer, the disc drives are
independently powered and are turned on and off from their own operator control
panels. Once a pack (or a pair of packs in the case of the Model 42) is mounted
and the power is on, the operator starts the pack rotating by moving the START /
STOP switch on the operator control panel to the START position. When the pack
is rotating at an acceptable operational speed (2400 rpm ± 2%), the READY indi-
cator light on the operator control panel turns on. With the power on, the disc
dri ve is in either of two states, called local and on-line.
When in local, the disc drive is disconnected from the central processor.
When on-line, the disc drive can perform read and write operations in response
to Read and Write instructions executed in the central processor.
The ENAB LE/DISAB LE switch on the operator control panel serves as a com-
bined ON LINE and LOCAL switch. When the' ENABLE/DISABLE switch is in
the DISABLE position, the disc drive is in local. When the READY light is on
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1-2 Models 40 and 42 Reference Manual

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General Description
and the ENABLE/DISABLE switch is in the ENABLE position, the disc drive is
on-line.
The Models 40 and 42 Disc Drives operate within the specifications shown in
Table 1-1.
Table 1-1. Specifications
Dimensions
Width Depth
Height
Inches
30-1/4
24 38
Centimeters
77
61 97
Minimum Service Clearances
Front
Rear
Right Left
Inches
36
36 0 0
Centimeters
91 91 0 0
Approximate Weight
Floor 321 lbs (without 10 lb disc pack)
146 kg (without 4.5 kg disc pack)
Maximum Heat Output/Hour
Electrical Requirements
Voltage Range
Frequency
Current
Maximum Current Surge
Phases
KVA
Operating Environment
Temperature
Relative Humidity
Non-Operating (Storage)
Environment
Temperature
Relati ve Humidity
3,9000 BTU
110-130V ± 10%
60 ± 1
Hz
9.6A
45A for 5 to 10 secs
single
1.1
982.8 kcal
208-230V ± 10%
50 ± 1 Hz
5.0A
25A for 5 to 10 secs
single
1.1
65 to 85°F 18 to 29.5
0C
20
to 75%
-30 to + 150°F
-34 to +660C
8 to 80%
Models 40 and 42 Reference Manual 1-3

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2 OPERATOR CONTROL PANEL
The operator control panels of the Models 40 and 42 Disc Drives (Figure 2-1)
comprise three toggle switches and three indicator lights. The function of each
switch and light is discussed in Table 2-1.
Figure 2-1. Operator Control Panel
Models 40 and 42 Reference Manual 2-1

Operator Control Panel
Table 2-1. Operator Control Panel
Control Function
POWER ON/POWER OFF Switch Turns the power on and off.
POWER Indicator Light
Illuminated whenever the power is on.
ENABLE/DISABLE Switch
When the READY light is on and this
switch is in the ENABLE position, the
disc drive is on -line. If this switch is in
the DISABLE position, the disc drive is
in local.
START/STOP Switch When this switch is moved to the START
position, the disc pack begins rotating, a
set of brushes cleans any dust from the
disc surfaces, and then the head assembly
emerges and positions itself at the outer-
most track. When this switch is moved to
the STOP position, the head assembly re-
tracts into the wall of the disc drive and
the pack slows to a halt.
READY Indicator Light Provided that no FILE UNSAFE condition
exists, the READY light is on whenever
the disc pack is rotating at the proper
speed (2400 rpm + 2%).
FILE UNSAFE Indicator Light The FILE UNSAFE light turns on when-
ever the disc drive detects a malfunction
which could conceivably result in loss of
recorded data. When the FILE UNSAFE
light turns on, any read or write opera-
tion currently in progress is terminated
immediately, and the disc drive cannot
-respond to any further instructions. To
turn off the FILE UNSAFE light, the
operator must move the START/STOP
switch to the STOP position and then
(after the pack has slowed to a halt) move
the START/STOP switch back to the
ST ART position.
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2-2 Models 40 and 42 Reference Manual

3 INSTRUCTION FORMAT
READ AND WRITE INSTRUCTIONS
A Read or Write instruction which addresses a disc drive has the following
characteristics:
• Both the LA-field and the LB-field must be zero.
• The A -field specifies the address of a 100-location segment of memory.
For a Read instruction, the segment is the input area into which the
record will be read. For a Write instruction, the segment is the output
area from which the record will be written.
• The B -field specifies the address of a six-character segment of memory.
The segment contains a six-character disc address (discussed as a
separate topic below) .
• Both the A -field and B -field may be modified by the contents of an
index register if the programmer so desires.
SIX-CHARACTER DISC ADDRESS
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The six-character segment of memory which is pointed to by the B-field of the
Read or Write instruction contains the following pieces of information~
• The disc drive device number (0-9).
• The arm number (0-4; on the Model 40, 0 specifies the top arm; on the
Model 42, 0 specifies the bottom arm).
• The track number (000-199, where 000 specifies the outermost track) .
• The sector number (00-99, where sectors 00-49 are accessed by the
upper head and sectors 50-99 by the lower head).
The format of the six-character disc address is shown in Figure 3-1.
Models 40 and 42 Reference Manual 3-1

Instruction Format
Only the numeric portions (1-4) of each character are used for specifying this
information. Bit 7 may be either 0 or 1; bit 5 must always be 1. The informa-
tion is specified as follows:
I CHARACTER
1
\(&3
! 4 5 6
Bit
D A T T S S 4
D A T T S S 3
D A T T S S 2
D T T T S S 1
(2)DEVICE NUMBER (0-9)
r0 HUNDREDS DIGIT (0 or 1) OF A
L.:..I THREE DIGIT TRACK NUMBER
f5\ TENS DIGIT (0-9) OF A TWO
L./DIGIT SECTOR NUMBER
~ TENS DIGIT (0-9) OF A THREE
~DIGIT TRACK NUMBER
r0 UNITS DIGIT (0-9) OF A THREE
l!IDIGIT TRACK NUMBER
NOTE:
f6\UNITS DIGIT (0-9) OF A TWO
L.iDIGIT SECTOR NUMBER
[0ARM NUMBER (0-4)
• The bits in characters 1,3,4,5, and 6 have the following values:
Bit 1 has the value 1 when it is ON.
Bit 2 has the value 2 when it is ON.
Bit 3 has the value 4 when it is ON.
Bit 4 has the value 8 when it is ON.
•
The bits in character 2 have the following values:
Bit 1 has the value 1 when it is ON.
Bit 2 has the value 1 when it is ON.
Bit 3 has the value 2 when it is ON.
Bit 4 has the value 4 when it is ON.
Figure 3-1. Six-Character Disc AddreSS
3 -2 Models 40 and 42 Reference Manual
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1
4 WRITE OPERATIONS
A Write instruction which addresses a disc drive causes 100 characters to be
accessed from memory and written onto a sector.
1
If a Write instruction addresses a disc drive which is not on-line, the instruc-
tion is terminated and Condition Codes 4 and 1 (Fault) in the central processor
are set on.
When attached to the Disc Controller of a System Ten computer, the Models 40
and 42 Disc Drives automatically performed a "read after write" to check for
errors. After a record (100 characters) has been written, the next time the
sector passes the read/write heads the sector is read and compared against
the Write instruction's output area. If the content of the sector exactly matches
the content of the Write instruction's output area, the write operation is con-
sidered successful. If the operation is unsuccessful, writing (and reading) is
repeated up to two more times. If, after a total of three attempts, the write
operation still has not been successfully performed, the sector is marked ''bad,''
the operation is terminated, and Condition Code 3 (Flag) in the central processor
is set on.
If a Write instruction addresses a Model 42 Disc Drive and the requested
sector is one which would be accessed by the middle arm (arm 2), the instruc-
tion is terminated and Condition Code 3 (Flag) in the central processor is set
on.
If a FILE UNSAFE condition occurs during a write operation, the operation is
terminated and Condition Codes 4 and 1 (Fault) in the central processor are
set on.
NOTE: If the Disc Controller is addressed by a Write Control instruction,
the instruction is acted upon as though it were a Write instruction.
A write operation also records the track address on the particular sector. This track
address is used for track address verification during disc read operations.
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Models 40 and 42 Reference Manual 4-1

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5 READ OPERATIONS
A Read instruction which addresses a disc drive causes the 100 characters
contained in a sector to be read into main memory.
If a Read instruction addresses a disc drive which is not on-line, the instruction
is terminated and Condition Codes 4 and 1 (Fault) in the central processor are
set on.
If the specified sector cannot be successfully read, reading is retried up to
three more times. If, after a total of four attempts, the sector still cannot be
successfully read, the operation is terminated and Condition Code 1 (Error) in
the central proces sor is set on.
If a Read instruction addresses a Model 42 Disc Drive and the requested sector
is one which would be accessed by the middle arm (arm 2), the operation is
terminated and Condition Code 3 (Flag) in the central processor is set on.
If a FILE UNSAFE condition occurs during a read operation, the operation is
terminated and Condition Codes 4 and 1 (Fault) in the central processor are set
on.
Track address verification is performed automatically at the beginning of a
System Ten disc read operation.
If an attempt is made to read a sector which has been marked ''bad'' or if
address verification reveals that the sector has not been initialized, the opera-
tion is terminated and Condition Code 3 (Flag) in the central processor is set
on.
If address verification reveals that the read/write heads have been positioned
at the wrong track, the operation is terminated, Condition Code 1 (Error) in
the central process is set on, and the read/write head mechanism is repositioned
to the outermost track (track 000).
NOTE:
If the Disc Controller is addressed by a Read Control instruction, the
instruction is acted upon as though it were .a Read instruction.
Models 40 and 42 Reference Manual 5-1

6 MULTI-PARTITION CONSIDERATIONS
A disc drive is free for use if it is not bound to a partition. A disc drive is
bound to a partition as soon as the partition initiates a seek 1 upon that drive. A
drive which is bound to a partition remains so until the associated input or out-
put operation is complete. When a disc drive is bound to a partition, no other
partition may initiate a seek upon that drive.
In an installation containing several disc drives, all the drives may be per-
forming seeks simultaneously; however, only one drive may be transmitting
data at a time.
The Disc Controller remembers which disc drives are bound to which partitions.
If several seeks are being performed simultaneously, the first partition to gain
control of the central processor after that partition's seek is complete pre-
empts the F AC for data transmission. Once data transmission is begun, the
partition may read and/or write sectors as long as the partition maintains
control of the central processor and does not try to move the read/write head
mechanism to another track. If the partition attempts to move the read/write
head mechanism, the partition relinquishes control of the central processor
and the disc drive is freed.
If an instruction addresses a disc drive which is bound to another partition, the
partition in which the instruction is executed relinquishes control of the central
processor and does not regain control until the disc drive is free.
If an instruction addresses a disc drive which is free but the operation requires
that the read/write head mechanism be moved, the seek is initiated (the drive
becomes bound) and the partition in which the instruction is executed relin-
quishes control of the central processor and does not regain control until the
seek is complete.
1 The term "seek" refers to the act of moving the read/write head mechanism to the
proper track in response to a Read or Write instruction executed in the central
processor.
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Models 40 and 42 Reference Manual 6-1

7 TIMING CONSIDERATIONS
Table 7-1 shows some of the more important operational timings for the
Models 40 and 42 Disc Drives.
Table 7 -1. Timings
Rotation Time
25.0 ms.
Arm Positioning Times
Minimum
2.5 ms.
Average 73.0 ms.
Maximum
135.0 ms.
Minimum arm positioning time is the amount of time required to move the read/
wri te head mechanism from one track to the next sequential track. A verage arm
positioning time is the amount of time required to move the read/write mecha-
nism from track 000 to track 099. Maximum arm positioning time is the amount
of time required to move the read/write head mechanism from tack 000 to
track 199.
Once the read/write head mechanism is positioned at the proper track, a read
operation takes 0.5 to 25.5 ms. These figures include the rotational delay time 1
(0 to 25 ms.) and the time needed to read a sector (0.5 ms.). If retries are
necessary, each retry takes 25 ms.
Once the read/write head mechanism is positioned at the proper track, a write
operation takes 26.5 to 51.5 ms. These figures include:
• the rotational delay time (0 to 25 ms.)
• the amount of time required for the Disc Controller to execute a special
timing algorithm (1 ms.)
• the amount of time required to write a sector (0.5 ms.)
• the amount of time required to rotate to the sector and then to read
the sector (25 ms.).
1 Rotational delay time is the amount of time needed for the desired sector to move to
the read/write heads.
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Models 40 to 42 Reference Manual
7-1

Timing Considerations
The disc is formatted as shown in Figure 7 -1.
63 73 83 93
61
51
95
90
56
66
98 88 78 68
NOTE: Sector 0-49 are accessed by the upper head on each arm, and sectors
50-99 are accessed by the lower head.
Figure 7-1. Disc Sector Layout
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7 -2 Models 40 to 42 Reference Manual

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Timing Considerations
After reading or writing a sector, the first subsequent sector on the same track
which may be read or written without requiring an additional revolution of the
disc is the fifth sector following the one read or written. Notice that the disc is
formatted such that sector 2 is the fifth sector following sector 1, sector 3 is
the fifth sector following sector 2, etc. This means that it is very efficient to
read and write a series of consecutively numbered sectors.
When performing any of the pairs of read/write operations shown in Table 7-2
using consecutively numbered sectors (e.g., sectors 1 and 2, 48 and 49, etc.) on
the same track, it takes 2 ms. for the second sector to move to the read/write
heads after the first operation is finished. If the two disc I/O instructions are
executed consecutively, the entire 2 ms. is wasted time. However, if computa-
tional instructions are inserted between the two disc I/O instructions, the
amount of time wasted can be significantly reduced. The figures shown in the
right column of Table 7 -2 specify the absolute maximum amount of time avail-
able for computation be~een the two disc I/O instructions. If the times are
exceeded, an additional revolution of the disc (25 ms.) will be required for the
second operation.
Table 7 -2. Overlap Timings
Read
Re!:lrl
.-., ---
Write
Write
Write
Read
Read
Write
1.6 ms.
.6 ms.
1.6 ms.
.6 ms.
NOTE: The Disc Controller takes 1 ms. to perform the special timing
algorithm at the start of a write operation. Therefore, only 0.6 ms. is
available for computation when a Write instruction is the second in the
pair of disc I/O instructions.
Models 40 to 42 Reference Manaul 7-3

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8 OPERATING INSTRUCTIONS
The Models 41, 41A, and41B Disc Packs each have their own carrying cases.
See Figure 8-1, 8-2, and 8-3.
To mount a disc pack (Model 41) on a Model 40 Disc Drive, proceed as follows:
a. Lift the carrying case by the top handle.
b. Holding the pack upside down, turn the knob on the bottom of the case
counterclockwise until the bottom of the case comes off.
c. Place the pack on the spindle in the center of the disc pack compartment.
d. Turn the handle on the top of the case clockwise.
e. When the handle will no longer turn, lift the case out of the compartment.
Figure 8-1. Top View of a Model 41B Disc Pack in Its Carrying Case
(Model 41 is identical except for identification marking)
Models 40 to 42 Reference Manual 8-1