Seagate ST12400N User manual

Product Manual, Volume 1
Hawk 2 Family:
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ST12400N/ND/NC
ST11900N/ND/NC

ST11900N/ND/NC
Product Manual, Volume 1
ST12400N/ND/NC
Hawk 2 Family:
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1995 SeagateTechnology, Inc.All rights reserved
Publication Number: 77767450, Revision E
March 1995
Seagate, SeagateTechnologyand the Seagate logo are registered trademarks of SeagateTechnology, Inc.
Hawk™, SeaFAX, SeaFone, SeaTDDand SeaBOARDare trademarks of Seagate Technology, Inc.
Other product names are registered trademarks or trademarks of their owners.
Seagate reserves the right to change, without notice, product offerings or specifications.No part of this publica-
tion may be reproduced in any form without written permission of SeagateTechnology, Inc.

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. E v
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Revision status summary sheet
Revision Authority Date Writer/Eng. Sheets Affected
A Issue 9/27/93 D. Ashby v thru viii, 1 thru 71.
B PLD: 84283 94 Mar 07 SS v thru viii, 1 thru 71.
(technical changes pages 46, 47,
52, 53 and 54.)
C PLD: 84224 5/26/94 SS v, vi, 6, 8, 11, 12, 15, 16, 21, 23, 24, 25,
29, 30, 31, 34, 35, 37, 46, 47, 51 - 54,
56, 60, 64.
D PLD: 84392 6/14/94 D. Ashby v, 2, 14 and 26.
E PLD: 84542 03/17/95 J. Rust/J. Bentley v, 24, 25, 69, 70, 71
Notice.
Product Manual 77767450 isVolume 1 of a twoVolume document with the SCSI interface information in
theVolume 2 SCSI Interface Product Manual, P/N 77738479.
If the SCSI Interface information is needed theVolume 2 Interface Manual should be ordered,P/N 77738479.

vi Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. C
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Table of contents
1.0 Scope........................................................................................................................................... 1
2.0 Applicable standards and reference documentation............................................................... 2
2.1 Standards ........................................................................................................................ 2
2.2 Applicable reference documents...................................................................................... 2
3.0 General description .................................................................................................................... 3
4.0 Standards features ..................................................................................................................... 5
4.1. Performance .................................................................................................................... 5
4.1.1 Reliability ............................................................................................................ 5
4.2 Unformatted and formatted capacities ............................................................................. 6
4.3 Options (factory installed) ................................................................................................ 6
4.4 Optional accessories (user installed) ............................................................................... 6
4.5 Installation........................................................................................................................ 7
5.0 Performance characteristics...................................................................................................... 8
5.1 Internal drive characteristics (transparent to user) ........................................................... 8
5.2 SCSI drive Seek, Read andWrite performance characteristics (Visible to User) ............. 8
5.2.1 Seek command execution time ........................................................................... 8
5.2.2 Format drive command execution time ............................................................... 9
5.2.3 Read data command execution time................................................................... 9
5.2.4 Write data command execution time ................................................................... 9
5.3 Generalized performance characteristics ........................................................................ 10
5.3.1 Notes for sections 5.2 and 5.3 ............................................................................ 11
5.4 Start/stop time 11
5.5 Prefetch/multi segmented cache control .......................................................................... 12
5.5.1 Cache operation.................................................................................................. 12
5.5.2 Prefetchoperation............................................................................................... 13
5.6 Caching write data ........................................................................................................... 14
5.7 Synchronized spindle operation ....................................................................................... 14
6.0 Reliability specifications ............................................................................................................ 18
6.1 Error rates........................................................................................................................ 18
6.1.1 Read errors ....................................................................................................... 18
6.1.2 Environmentalinterference................................................................................ 18
6.1.3 Write errors ....................................................................................................... 19
6.1.4 Seek errors........................................................................................................ 19
6.2 Reliability and service ...................................................................................................... 19
6.2.1 Mean time between failure................................................................................. 19
6.2.2 Preventive maintenance .................................................................................... 19
6.2.3 Service life......................................................................................................... 19
6.2.4 Service philosophy ............................................................................................ 20
6.2.5 Installation ......................................................................................................... 20
6.2.6 Service tools...................................................................................................... 20
6.2.7 Product Warranty............................................................................................... 20

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B vii
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Table of contents
7.0 Physical/electrical specifications .............................................................................................. 21
7.1 AC power requirements ................................................................................................... 21
7.2 DC power requirements ................................................................................................... 21
7.2.1 Conducted noise immunity ................................................................................ 22
7.2.2 Power sequencing............................................................................................. 22
7.2.3 12 V - current profile.......................................................................................... 22
7.3 Heat/powerdissipation..................................................................................................... 23
7.4 Environmentallimits......................................................................................................... 23
7.4.1 Temperature ...................................................................................................... 24
7.4.2 Relative humidity ............................................................................................... 26
7.4.3 Effective altitude (sea level ref).......................................................................... 26
7.4.4 Shock and vibration........................................................................................... 26
7.4.5 Air cleanliness ................................................................................................... 28
7.5 Electromagneticcompatibility........................................................................................... 28
7.5.1 Electromagneticsusceptibility ........................................................................... 28
7.6 Mechanical specifications ................................................................................................ 29
7.6.1 Drive orientation ................................................................................................ 31
7.6.2 Cooling .............................................................................................................. 31
7.6.3 Drive mounting .................................................................................................. 31
8.0 Media characteristics ................................................................................................................. 32
8.1 Media description............................................................................................................. 32
9.0 Defect and error management ................................................................................................... 33
9.1 Drive internal defects/errors............................................................................................. 33
9.2 SCSI systems error considerations.................................................................................. 33
10.0 Option/configuration headers.................................................................................................... 34
10.1 Drive ID/option select header........................................................................................... 34
10.2 Synchronized spindles interface ...................................................................................... 37
10.2.1 electrical description.......................................................................................... 37
10.3 Grounding........................................................................................................................ 38
11.0 Interface requirement ................................................................................................................. 39
11.1 General description.......................................................................................................... 39
11.2 SCSI interface messages supported................................................................................ 39
11.3 SCSI interface commands supported .............................................................................. 40
11.3.1 Inquiry data ....................................................................................................... 42
11.3.2 Mode sense data............................................................................................... 43
11.4 SCSI bus conditions and miscellaneous features supported............................................ 48
11.5 Synchronous data transfer............................................................................................... 49
11.5.1 Synchronous data transfer periods supported ................................................... 49
11.5.2 REQ/ACK offset ................................................................................................ 49
11.6 Physical interface............................................................................................................. 49
11.6.1 DC cable and connector.................................................................................... 51
11.6.2 Physical characteristics ..................................................................................... 51
11.6.3 Connectorrequirements.................................................................................... 53
11.6.4 Electrical description ......................................................................................... 60
11.7 Disc drive timing .............................................................................................................. 65

viii Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B
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Table of contents
12.0 Options........................................................................................................................................ 67
12.1 Front panel....................................................................................................................... 67
12.2 Single unit shipping pack ................................................................................................. 67
13.0 Accessories ................................................................................................................................ 68
13.1 Front panel kit .................................................................................................................. 68
13.2 Installationmanual ........................................................................................................... 68
14.0 Technical support services ........................................................................................................ 69
Seagate Peripheral Family ...................................................................................................................... 70

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B 1
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1.0 Scope
This specification describes the SeagateTechnology, Inc.Hawk 2 Model ST12400 Disc Drive.This high capacity,
highperformancemember ofthe Seagate 3.5inch rigiddisc family has anew HDA(Head/Disc Assembly)design
having improvements over previous 3.5-inch Seagate models.It has an embedded SCSI controller.Performance
information is given in Section 5. The Hawk 2 Family Model ST12400 drive interface is defined for functional
compatibility to a subset of the Seagate SCSI-2 Interface Specification 77738479, and the ANSI SCSI-2 stan-
dard.The Hawk 2 Family drives are classified as “Intelligent” peripherals.The Hawk 2 Family provides Level 2
conformance (highest level) with the ANSI SCSI-1 standard.Details of the Hawk 2 Family drive SCSI implemen-
tationareprovidedin Section 11ofthis specification, (Vol.1) andinthe SCSI-2/SCSI-3 InterfaceProductManual
P/N 77738479 (Vol. 2; Ver. 2).
The Hawk 2 family of drives consists of the ST12400N/ND/NC and ST11900N/ND/NC drives.
From this point on in this Product Manual the reference to Hawk 2 Family is referred to as “the drive” (unless
reference to individual models are necessary).
The drive printed circuit board is referred to as a PCB.
Figure 1-1. Hwk 2 family drive
SEAGATE
50 pin SCSI I/O and 4 pin DC power connector shown. "NC" drive models have a
single 80 pin connector and no separate DC power connector.
*
*

2 Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. D
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2.0 Applicable standards and reference documentation
The drive has been developed as a system peripheral to the highest standards of design and construction.The
drive depends upon its host equipment to provide adequate power and environment in order to achieve optimum
performance and compliance with applicable industry and governmental regulations. Special attention must be
given in the areas of safety, power distribution, shielding, audible noise control, and temperature regulation. In
particular, the drive must be securely mounted in order to guarantee the specified performance characteristics.
2.1 Standards
The Hawk 2 Family complies with Seagate standards as noted in the appropriate sections of this specification
and the Seagate SCSI-2/SCSI-3 Interface Specification, P/N 77738479 (Vol. 2, Version 2).
The Hawk 2 Family is a UL Recognized component per UL 1950 and a CSA Certified component per CAN/CSA-
C22.2 No. 950-M89. It also meets the requirements of DIN VDE 0805/05.90 and EN60950: 1988 (IEC 950).
The Hawk 2, as delivered, is designed for system integration and installation into a suitable enclosure prior to
use. As such the Hawk 2 is supplied as a sub-assembly and is not subject to Subpart J of Part 15 of the FCC
Rules and Regulations nor the Radio Interference Regulations of the Canadian Department of Communications.
However, the unit has been tested using proper shielding and grounding and found to be compliant with Class A
limits of the FCC Rules and the Regulations ofThe Canadian Department of Communications.
The physical design characteristics of the Hawk 2 serve to minimize radiation when installed in an enclosure that
provides reasonable shielding.As such, the Hawk 2 is capable of meeting the Class B limits of the FCC Rules
andRegulationsof the CanadianDepartment ofCommunication.However, itis the usersresponsibilityto assure
that the Hawk 2 meets the appropriate EMI requirements in their system. Shielded I/O cables may be required if
the enclosure does not provide adequate shielding. If the I/O cables are external to the enclosure, shielded
cables should be used, with the shields grounded to the enclosure and to the host controller.
Caution. To avoid potential service problems, observe the following precautions:
The Manufacturers installed labels must not be removed from the drive or covered with additional
labels, as they contain information required when servicing the product.
2.2 Applicable reference documents
Installation Guide Seagate P/N 77767451
Product Manual - SCSI-2 Interface Seagate P/N 77738479
ANSI Small Computer System Interface (SCSI): Document Number ANSI3.131-1986 (X3T9/84.40 Rev. 1B)
(X3T9.2/82-2 Rev. 17B) and X3T9.2/86-109 Revision 10H (SCSI-2).
PackageTest Specification Seagate P/N 30190-001 (under 100 lb.)
PackageTest Specification Seagate P/N 30191-001 (over 100 lb.)
In case of conflict between this document and any referenced document, this document shall take precedence.

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B 3
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3.0 General description
The drives are a member of a family of low cost, high performance, highly reliable, random access storage
devices designed to meet the needs of the OEM marketplace.
The drive records and recovers data on ten 3.7 inch (95 mm) fixed discs.
The drive supports the Small Computer System Interface-2 (SCSI-2) as described in the ANSI SCSI and SCSI-
2 Interface Specifications to the extent described in this product specification (Vol.1), which defines the product
performancecharacteristicsof theHawk2Family ofdrives,andtheSCSI-2InterfaceProductManualP/N77738479
(Vol.2,Version 2) which describes the general interface characteristics of this and other families of Seagate 3.5-
inch drives.
The drive interface supports multiple initiators, disconnect/reconnect, self configuring host software and auto-
matic features that relieve the host from the necessity of knowing the physical characteristics of the targets
(logical block addressing is used).
The Head/Disc Assembly (HDA) is environmentally sealed at the factory.Air recirculates within the HDA through
a nonreplaceable filter to maintain a contamination free head/disc environment.
Refer to Figure 3.0-1 for an exploded view of the drive. NEVER disassemble the Head/Disc Assembly (HDA).
This exploded view is for information only.Do not attempt to service items in the sealed environmental enclosure
(heads, media, actuator, etc.) as this requires special facilities.The drive contains no parts replaceable by the
user.The drive warranty is voided if the HDA is opened.
The Hawk 2 Family drives use a dedicated landing zone at the innermost radius of the media to eliminate the
possibilityof destroyingordegradingdata bylanding inthedata zone.Thedriveautomatically goesto the landing
zone when the power is removed.
The Hawk 2 Family drives incorporate an automatic shipping lock which prevents potential damage to the heads
and discs that result from movement during shipping and handling.The shipping lock disengages when power is
applied to the drive and the head load process begins.
The Hawk 2 Family drives decode Track 0 location from the dedicated servo surface to eliminate mechanical
transducer adjustments and related reliability concerns.
The Hawk 2 Family drives use a high performance actuator assembly that consists of a low inertia, balanced,
patented, straight arm design that provides excellent performance with minimum power dissipation.

4 Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B
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Figure 3.0-1. Hawk 2 family drive
ST12400N/ND
Family PCB ST12400NC Family PCB

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B 5
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4.0 Standard features
The Hawk 2 Family has the following standard features:
•Integrated SCSI Controller
•Single Ended and Differential SCSI drivers and receivers
•Asynchronous and Synchronous data transfer protocol
•Firmware downloadable via SCSI interface
•Selectable sector size from 256 to 4096 bytes/sector
•Programmable sector reallocation scheme
•Flawed sector reallocation at format time
•Programmable auto write and read reallocation
•Reallocation of defects on command (Post Format)
•96 bit Reed-Solomon error correcting code
•Sealed Head/Disc Assembly
•No preventative maintenance or adjustment required
•Dedicated head landing zone
•Automatic shipping lock
•AutomaticThermal Compensation
•PatentedTri-Phase Servo with embedded Grey Code track address to guarantee servo positioning.
•Self diagnostics performed at power on
•1:1 Interleave
•Zoned Bit Recording (ZBR)
•Vertical, horizontal, or top down mounting
•Dynamic spindle brake
•Synchronous spindle capability
•256 K byte data buffer (Optional 1 MB available)
•Permanently mounted terminators (for model ST12400N only), enabled by installation of a jumper plug.
4.1 Performance
•Programmable multi-segmentable cache buffer
•5411 RPM Spindle.Average latency = 5.54 ms
•Command Queuing of up to 64 commands per initiator
•Background processing of queue
•Supports start and stop commands
•Provides synchronized spindle capability
•Low audible noise for office environment
•Low power consumption
4.1.1 Reliability
•500,000 hour MTBF
•Adaptive seek velocity. Improved seek performance
•LSI circuitry
•Balanced low mass rotary voice coil actuator
•5 year warranty

6 Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. C
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4.2 Unformatted and formatted capacities
Formatted capacity depends on the number of spare reallocation sectors reserved and the number of bytes per
sector.The following table shows some typical formatted capacities.
Spare Sectors or Cylinders ST12400N/ND/NC ST11900N/ND/NC
Reserved for reallocation 512[1] 1024[1] 512[1] 1024[1]
MB MB
No Spares 2165 2279 1709 1799
12 Spare Sectors Per Cylinder [2]
2 Spare Cylinders per Unit [3] 2148 2245 1700 1758
One Spare Sector per Cylinder
2 Spare Cyl. per Unit [3] 2162 2275 1707 1795
Unformatted Capacity 2537 2003
Notes.
[1] Bytes per sector. Sector size selectable at format time.Users having the necessary equipment may modify
the data block size before issuing a format command and obtain different formatted capacities than those
listed. User available capacity depends on spare reallocation scheme selected. See Mode Select Command
and Format Command in the SCSI Interface Product Manual P/N 77738479.
[2] Twelve spare sectors are on one track.ST11900 has 6 spare sectors per cylinder.
[3] Spare cylinders are on the inner tracks.
The standard OEM model is as follows:
Formatted Data Block Size* Unformatted
512 Byte/Sector
ST12400N/ND/NC 2148 MB 2537 MB
ST11900N/ND/NC 1700 MB 2003 MB
*Twelve spare sectors per cylinder, two spare cylinders/unit for ST12400
Six spare sectors per cylinder, two spare cylinders/unit for ST11900
4.3 Options (factory installed)
The capacities shown in paragraph 4.2 are available upon request. Other capacities can be ordered depending
on sparing scheme and sector size requested.
The following options are incorporated at the time of production. See Section 12.0.
•Front panel (green LED) - See Figure 3.0-1
•Installation Manual P/N 77767451
4.4 Optional accessories (user installed)
The following accessories are available.All kits may be installed in the field. See Section 13.0.
•Front Panel Kit (with green LED) - See Figure 3.0-1
•Single Unit shipping pack kit
•Installation Guide P/N 77767451
•Adapter Accessory Frame Kit P/N 75790701 (adapts 3.5-inch drive to fit in 5.25-inch drive mounting
space)

Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. B 7
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4.5 Installation
For option jumper locations and definitions refer to Figure 10.1-1. Drive default mode parameters are not nor-
mally needed for installation.Refer to Section 11.3.2 for default mode parameters if they are needed.
•Ensure that the SCSI ID of the drive is not the same as the host adapter.Most host adapters use SCSI ID 7.
•If multiple devices are on the bus set the drive SCSI ID to one that is not presently used by other devices on
the bus.
•If the drive is the only device on the bus, attach it to the end of the SCSI bus cable. Permanently installed
terminatorsmustbe enabled onthe drive forST12400N models usinga jumper plug(seeFigure 10.1-1), For
ST12400ND models, terminators must be installed external to the drive.These external terminators must be
provided by the user, systems integrator or host equipment manufacturer.
•Ifthe drive isattachedto abusthat containsotherdevices, andthenew driveisnot attachedtothe endofthe
bus, the terminator enable jumper should be removed from the new drive.
•Setall appropriate optionjumpers for desiredoperation prior topower on.Ifjumpers arechanged after power
has been applied, recycle the drive power to make the new settings effective.
Installation instructions are provided by host system documentation or with any additionally purchased drive
installation software. If necessary see section 14.0 for Seagate support services telephone numbers.
Formatting
•It is not necessary to low level format this drive.The drive is shipped from the factory low level formatted in
512 byte sectors.
•Reformat the drive if one of the following occurs.
- A different sector size is selected.
- A different spare sector allocation scheme is selected.

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5.0 Performance characteristics
5.1 Internal drive characteristics (transparent to user)
ST12400N/ND/NC ST11900N/ND/NC
Drive Capacity 2537 2003 MByte (UNF)
Read/Write Heads 19 15 Data (Max)
Bytes/Track 50,945 50,945 Bytes (Avg)
Bytes/Surface 131.3 131.3 Mbytes (UNF)
Tracks/Surface, Total 2621 2621 Tracks (user
accessible)
Tracks/Inch 3000 3000 TPI
Servo Heads 1 1
Internal Data Rate 26.8 to 45.6 26.8 to 45.6 Mbits/sec
(variable with
zone)
Disc Rotational Speed 5411+0.5% 5411+0.5% r/min
Average Rotational Latency 5.54 5.54 ms
5.2 SCSI Seek, Read andWrite performance characteristics (visible to user) [8]
Refer to Section 11.7 and to the SCSI-2 Interface Product Manual 77738479 for additional timing details.
5.2.1 Seek time Drive Level
ST12400N/ND/NC ST11900N/ND/NC
Read Write Read Write
ms ms
Average - Typical [3]* 9.3 10.8 9.3 10.8
Max. [2] 11.1 12.6 11.1 12.6
Single Track - Typical [3] 1.0 1.7 1.0 1.7
Max. [2] 1.5 2.0 1.5 2.0
Full Stroke - Typical [3] 21.0 22.5 21.0 22.5
Max. [2] 23.0 24.0 23.0 24.0
Including Controller Overhead
(without disconnect) [1] [4]
ST12400N/ND/NC ST11900N/ND/NC
Read Write Read Write
ms ms
Average - Typical [3] 10.3 11.8 10.3 11.8
Max. [2] 12.1 13.6 12.1 13.6
Single Track - Typical [3] 2.0 2.7 2.0 2.7
Max. [2] 2.5 4.0 2.5 4.0
Full Stroke - Typical [3] 22.0 23.5 22.0 23.5
Max. [2] 24.0 25.0 24.0 25.0

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5.2.2 Format drive command execution time (minutes) [1]
ST12400N/ND/NC ST11900N/ND/NC
Maximum (with verify) 45 Min. 37 Min
Maximum (no verify) 31 Min. 27 Min.
*[ ] All notes are listed in Section 5.3.1.
5.2.3 Read data command execution time [4]
(512 byte sector size, without disconnect and with read look ahead cache disabled). latency
time is included.
a. From CDB reception to the drive request for the first data byte to be transferred to the Host
1. Typical (Zero Stroke Seek) 7.32 ms [3]*
2. Typical (Average Seek) 16.84 ms [3]
3. Maximum (Full Stroke Seek) 31.38 ms [2]
b. Single Sector Read andTransfer of data to Host (time from receipt of last byte of the CDB to the request for
a status byte transfer to Host) [7].
1. Typical (Zero Stroke Seek) 7.42 ms [3]
2. Typical (Average Seek) 16.95 ms [3]
3. Maximum (Full Stroke Seek) 31.49 ms [2]
5.2.4 Write data command execution time [4]
(512 byte sector size, without disconnect and with read look ahead disabled) latency time
is included.
a. From CDB reception to the request for the first byte of write data from the Host.
1. Typical 1.49 ms 2. Maximum 1.61 ms
b. Single Sector Write and Data Transfer from Host [7] [6]
(Time from receipt of the last byte of the CDB to the request for a completion status transfer to the Host)
1. Typical (Zero Stroke Seek) 7.72 ms [3]
2. Typical (Average Seek) 17.10 ms [3]
3. Maximum (Full Stroke Seek) 31.93 ms [2]
*[ ] All notes are listed in Section 5.3.1.

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5.3 Generalized performance characteristics
Minimum Sector Interleave 1 to 1
Data BufferTo/From Disc Media
Data transfer rate (< 1 sector) - 512 Byte Sector
Min. [4]* 3.35 MByte/sec
Avg. [4] 4.59 MByte/sec
Max. [4] 5.35 MByte/sec
Data BufferTo/From Disc Media
Data Transfer Rate (< 1 Track) - 512 Byte Sector
Min. [4] 2.88 MByte/sec divided by (Interleave Factor)
Avg. [4] 3.94 MByte/sec divided by (Interleave Factor)
Max. [4] 4.6 Mbyte/sec divided by (Interleave Factor)
SCSI Interface Data
Transfer Rate (Asynchronous) [5] ST12400N/NC/ST11900N/NC ST12400ND/ST11900ND
-MaximumInstantaneous ** 5.2 MBytes/sec 3.3 MBytes/sec
-Maximum Average *** 3.1 MBytes/sec 2.4 MBytes/sec
Sector Sizes 512 user data blocks (default)
Variable (256 to 4096) in even sector sizes
Synchronous Transfer Rate
From 1.25 MByte/sec to 10.0 MBytes/sec (See section 11.5.)
Read/Write consecutive sectors on a track Yes
Flaw reallocation performance impact (For flaws reallocated using the spare Negligible
sectors per track reallocation scheme.)
Flaw reallocation performance impact (For flaws reallocated using the spare Negligible
sectors per cylinder reallocation scheme.)
Flaw reallocation performance impact (For flaws reallocated using the spare tracks 35 ms (typical)
per volume reallocation scheme.)
Overhead time for head switch (512 byte sectors) 1 ms
Overhead time for one track cylinder switch <3 ms Typical
Average rotational latency 5.54 ms
* [ ] All notes are listed in Section 5.3.1.
** Assumes system ability to support 5.2 Mb/s and no cable loss.
*** Assumes typical host delays and cable losses.

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5.3.1 Notes for sections 5.2 and 5.3.
[1] Execution time measured from receipt of the last Byte of the Command Descriptor Block (CDB) to the re-
quest for a Status ByteTransfer to the Initiator (excluding connect/disconnect).
[2] Maximum times are specified over the worst case conditions of temperature, voltage margins and drive
orientation. When comparing specified seek times, care should be taken to distinguish between typical seek
times and maximum seek times.The best comparison is obtained by system benchmark tests conducted
under identical conditions.Maximum times do not include error recovery.
[3] Typical Seek values are measured under nominal conditions of temperature, voltage, and horizontal orienta-
tion as measured on a representative sample of drives.
[4] Assumes no errors and no sector has been relocated.
[5] Rate measured from the start of the first sector transfer to or from the Host.
[6] Assumes the Initiator immediately sendsWrite Data to the drive when requested.
[7] Command execution requires a data transfer phase (data to or from the disc media).Assumes the initiator is
instantly ready to send/receive the data when the drive generates first request for a data byte transfer, and
assumes an average data transfer rate between the drive and the Initiator as specified in section 5.3.
[8] Allperformance characteristics assumethatautomatic adaptivetemperaturecompensation isnotin process
when the SCSI command is received. A SCSI command being executed is not interrupted for automatic
adaptivetemperature compensation. Ifadaptivethermal compensationisin processwhena SCSIcommand
is received, the command is queued until the compensation for the specific head being compensated com-
pletes. When compensation completes for the specific head being compensated, the first queued SCSI
command is executed. When execution of the first queued command is complete, the drive continues the
compensation for the remaining head(s).The above procedure continues until compensation for all heads is
completed, or until one minute has elapsed. If the compensation for all heads is not complete in one minute,
the drive performs compensation for all of the remaining heads sequentially without any interruption. The
driveinitiates an automaticadaptive temperaturecompensationcycle approximatelyone minute afterpower-
on, and approximately once every 10 minutes thereafter. Automatic adaptive temperature compensation
takes less than 0.1% of bus time. Automatic temperature compensation also occurs at other times, but
should be transparent to the user (e.g., during format, Rezero Command, at spindle up, during read error
recovery, and during Reassign Block functions).A Rezero command can be used to reset the thermal com-
pensationtimer back toits start sothat the hostcan knowwhenthe interruptionfor thermal compensationwill
occur.
5.4 Start/stop time
After DC power has been applied, the drive becomes ready within 25 seconds if the Motor Start Option is dis-
abled (i.e. the motor starts as soon as the power has been applied). During this time the drive responds to some
commands over the SCSI interface*. Stop time is less than 20 seconds from removal of DC power.

12 Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. C
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If the Motor Start Option is enabled the internal controller accepts the commands listed in the SCSI Interface
ProductManual* lessthan 3 secondsafter DCpowerhasbeen applied.Afterthe MotorStartCommandhas been
received the drive becomes ready for normal operations within 25 seconds.The Motor Start Command can also
be used to command the drive to stop the spindle*.
There is no power control switch on the drive.
5.5 Prefetch/multi-segmented cache control
Thedriveprovides prefetch (readlook-ahead) and multi-segmentedcache control algorithmsthat in manycases
can enhance system performance. “Cache” as used herein refers to the drive buffer storage space when it is
used in“cache” operations.To select prefetch and cache features the host sends the Mode Select command with
the proper values in the applicable bytes in Mode Page 08h*. Prefetch and cache operation are independent
features from the standpoint that each is enabled and disabled independently via the Mode Select command.
However, in actual operation the prefetch feature overlaps cache operation somewhat as is noted in sections
5.5.1 and 5.5.2.
All default cache and prefetch Mode parameter values (Mode Page 08h) for standard OEM versions of this drive
family are given inTables 11.3.2-1 through 11.3.2-4.
5.5.1 Cache operation
In general, 240 Kbytes of the 256 Kbytes of physical buffer space in the drive can be used as storage space for
cache operations (984 Kbytes of 1 MB for drives having the optional 1 MB buffer).The buffer can be divided into
logical segments (Mode Select Page 08h, byte 13) from which data is read and to which data is written.The drive
maintains a table of logical block disk medium addresses of the data stored in each segment of the buffer. If
cache operation is enabled (RCD bit = 0 in Mode Page 08h, byte 2, bit 0. See SCSI Interface Product Manual*),
data requested by the host with a Read command is retrieved from the buffer (if it is there), before any disc
access is initiated. If cache operation is not enabled, the buffer (still segmented with required number of seg-
ments)is stillused, butonlyas circularbuffer segmentsduringdiscmedium readoperations(disregarding Prefetch
operation for the moment).That is, the drive does not check in the buffer segments for the requested read data,
but goes directly to the medium to retrieve it.The retrieved data merely passes through some buffer segment on
the way to the host. All data transfers to the host are in accordance with“buffer-full”ratio rules.See explanations
associated with Mod page 02h (disconnect/reconnect control) in the SCSI Interface Product Manual*.
The following is a simplified description of a read operation with cache operation enabled:
Case A - A Read command is received and the first logical block (LB) is already in cache:
1. Drive transfers to the initiator the first LB requested plus all subsequent contiguous LB’s that are already in
the cache.This data may be in multiple segments.
2. When the requested LB is reached that is not in any cache segment, the drive fetches it and any remaining
requested LB’s from the disc and puts them in a segment of the cache. The drive transfers the remaining
requested LB’s from the cache to the host in accordance with the disconnect/reconnect specification men-
tioned above.
3. If the prefetch feature is enabled, refer to section 5.5.2 for operation from this point.
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*SCSI Interface Product Manual P/N 77738479.