Hard Drive: QUANTUM: PRODRIVE LPS 270 S 270MB 3.5"/SL SCSI2 SE
P R O D R I V E L P S 2 7 0 S QUANTUM
Native| Translation
------+-----+-----+-----
Form 3.5"/SLIMLINE Cylinders 2740| | |
Capacity form/unform 270/ MB Heads 2| | |
Seek time / track 12.0/ 4.0 ms Sector/track | | |
Controller SCSI2 SINGLE-ENDED Precompensation
Cache/Buffer 128 KB LOOK-AHEAD Landing Zone
Data transfer rate 4.000 MB/S int Bytes/Sector 512
10.000 MB/S ext SYNC
Recording method RLL 1/7 operating | non-operating
-------------+--------------
Supply voltage 5/12 V Temperature *C 55 | -40 65
Power: sleep W Humidity % 5 85 | 5 95
standby 0.8 W Altitude km -0.200 3.000| -0.200 12.000
idle 3.6 W Shock g 10 | 60
seek 5.7 W Rotation RPM 4500
read/write 5.0 W Acoustic dBA 33
spin-up 13.2 W ECC Bit 112,REED SOLOMON
MTBF h 150000
Warranty Month
Lift/Lock/Park YES Certificates CSA,FCC,TUV,UL1950,VDE
Layout
QUANTUM PRODRIVE LPS 270/540S PRODUCT MANUAL 81-104075-01 AUG. 1993
+--------+-------------------------------------------------+
| | A0 A1 A2 |
| | JP2 +-+-+-++-+-+-+ ++ |XXJ1
| | +-+-+-++-+-+-+JP1 || |XX
++ | PO || |XXI
|+------++-+ SCSI || |XXN
| ++ | Terminator || |XXT
| | J3 ++ |XXE
| ++ | |.XR
|+------++-+ ++ |XXF
++ | || |XXA
| |+-+J5 SCSI || |XXC
| +-|| |Control Terminator || |XXE
| | |+-+Connector || |XX
| | | ++ |XX
| | | |
| +-|+-+J2 |XX Power
| | |+-+LED |XX
+------+-+-------------------------------------------------+
|
|
|
|
|
|
|
+---J5----+ +-J2+
|O O O O O| |O O|LED Connector
--+---------+-+---+----------------PCB-- Side View
| | | | + GND
| | | +-- A2
| | +---- A1
| +------ A0
+-------- RESERVED
Jumpers
QUANTUM PRODRIVE LPS 270/540S PRODUCT MANUAL 81-104075-01 AUG. 1993
Jumper Setting
==============
x = Factory default
Jumper Options
--------------
The configuration of three jumpers controls the drive's mode of
operation:
- A2, A1, A0 - SCSI Bus Identification Jumpers
- PO - Product Option
In addition to the hardware jumpers listed above, the ProDrive LPS
270/540S hard disk drive supports software control SCSI ID, Parity
Enable, Wait Spin, and Self-Seek as determined by Mode Page 39h.
The factory default is for the SCSI ID to be controlled by hardware
jumper A2, A1, and A0 of JP1, SCSI bus parity checking to be
controlled by hardware jumper PO, and the Wait/Spin option disabled.
If the PO jumper is removed, SCSI bus parity checking is disabled.
SCSI-Bus Device Identification Jumpers
--------------------------------------
Used in combination, the jumper settings across pins A2, A1, and A0
determine the ProDrive LPS 270/540S hard disk drive's SCSI-bus
device identification (SCSI ID). By default, Quantum configures the
drive with a SCSI ID of six; that is, with jumpers installed across
the pins labeled A2 and A1, and no jumper installed across the pins
labeled A0.
+----------+-----------------------+ | SCSI ID | Jumpers | | | A2 | A1 | A0 | +----------+-------+-------+-------+ | 0 | OPEN | OPEN | OPEN | | 1 | OPEN | OPEN | CLOSED| | 2 | OPEN | CLOSED| OPEN | | 3 | OPEN | CLOSED| CLOSED| | 4 | CLOSED| OPEN | OPEN | | 5 | CLOSED| OPEN | CLOSED| |x 6 | CLOSED| CLOSED| OPEN | | 7 | CLOSED| CLOSED| CLOSED| +----------+-------+-------+-------+
The SCSI bus supports up to eight devices, including the host system.
A device's identification number determines its priority and must be
unique in the system.
Product Option (PO) Jumper
--------------------------
The function of the PO jumper is determined by Mode Page 39. With the
PO jumper installed, one of the following functions can be
controlled:
- Wait Spin
- Enable Parity
- Self Seek
The default setting is that the PO jumper is installed and contolling
the Enable Parity function, which checks parity on the SCSI bus.
Wait/Spin (WS) Function
-----------------------
At a power on or reset, with the Wait/Spin option disabled, the
motor start to spin automatically, and the drive will become ready
to perform read or write operations without the need for a start
command.
At a power on or reset, with the Wait/Spin option enabled, the host
must send a START/STOP UNIT command to activate the drive motor. The
Wait/Spin option permits power sequencing, to prevent an overload of
the host's power supply due to simultaneous, peak start-up current
demands from multiple devices. Once the drive receives a START/STOP
UNIT command, it will become ready to perform read or write
operations.
A delayed startup without the need for a START command may also be
enabled as determined by Mode Page 39h.
Enable Parity (EP) Function
---------------------------
The Enable Parity (EP) option controls parity checking of data across
the SCSI bus. With parity checking enable (PO installed), the drive
performs parity checking. With parity checking disabled (PO removed),
the drive continues to generate parity information, but does not
perform parity checking.
Self-Seek (SS) Function
-----------------------
Self-Seek can be initiated by the PO jumper in conjunction with Mode
Page 39h, or the host can initiate a Self-Seek test by issuing a SEND
DIAGNOSTIC command, with the self-test bit set to one.
When power is applied to the drive with the Self-Seek test enabled,
the drive initiates a Self-Seek test. The SCSI-bus device identifica-
tion (SCSI ID) currently selected determined the Self-Seek test
performed. For information about selecting a SCSI ID see the section
"SCSI-Bus Device Identification Jumpers".
With the SCSI ID set to six, its default value, the drive performs
random seeks, verifying the cylinder ID after every seek. The random
seeks continue as long as power is applied to the drive or until the
drive encounters a seek error.
If the SCSI ID is set to any value other than six, the drive
executes seeks in a butterfly pattern.
Each butterfly seek pattern:
1. Start at cylinder zero.
2. Seeks to the last data cylinder.
3. Performs successive seeks over a progressively narrower range of
cylinders - incrementing by three at the lower limit of the range
and decrementing by three at the upper limit of the range - until
the drive seeks to the middle cylinder.
4. Performs successive seeks over a progressively wider range of
cylinders - decrementing by three at the lower limit of the range
and incrementing by three at the upper limit of the range.
5. Ends with a seek to cylinder zero.
Seek in this butterfly pattern continue as long as is applied to the
drive or until the drive encounters a seek error.
During the Self-Seek test, the drive can execute any command.
Quantum-Unique Drive Control Parameters, Page Code 39H ------------------------------------------------------ +--------+------+-----+-----+-----+-----+-----+-----+-----+ | |Bit 7 |Bit 6|Bit 5|Bit 4|Bit 3|Bit 2|Bit 1|Bit 0| +--------+------+-----+-----+-----+-----+-----+-----+-----+ |Byte 0 |RESERVED = 0| PAGE CODE = 39H | +--------+------------+-----------------------------------+ |Byte 1 | PAGE LENGTH = 06H | +--------+-----+------+-----+-----+-----+-----+-----+-----+ |Byte 2 |DIO |DII |FDB |RUEE |FDPE |R = 0|DUA |DRT | +--------+-----+------+-----+-----+-----+-----+-----+-----+ |Byte 3 |DDIS |DELDIS|RES=0|DPC |SSID | SCSIADR | +--------+-----+------+-----+-----+-----+-----+-----+-----+ |Byte 4 |PODIS|POSS |POEP |POWS |MDLY |SS |RES=0|WS | +--------+-----+------+-----+-----+-----+-----+-----+-----+ |Byte 5 | MOTOR DELAY TIME | +--------+------------------------------------------------+ |Byte 6-7| RESERVED = 0 | +--------+------------------------------------------------+
DIO - Disable Identify out (Byte 2, Bit 7)
------------------------------------------
When DIO is set to one, the drive does not require an IDENTIFY
message from the initiator to disconnect and reconnect. When DIO
is set to zero, the drive requires to send an IDENTIFY message prior
to disconnecting. The default is zero.
DII - Disable Identify IN (Byte 2, Bit 6)
-----------------------------------------
When DII is set to one, the drive does not send an IDENTIFY message
after reconnecting to an initiator. When DII is set to zero, the
drive sends an IDENTIFY message after reconnecting. The default is
zero.
FDB - Fast Deassertion of Busy (Byte 2, Bit 5)
----------------------------------------------
This parameter is neither used nor required by applications using the
drive. It is ignored. The default value is zero.
RUEE - Reallocate Uncorrectable Error Enable (Byte 2, Bit 4)
------------------------------------------------------------
When RUEE is set to one and the ARRE bit in page 1 of the error-
recovery parameters is set, the drive automatically writes data
containing uncorrectable, hard errors to a different logical block
and appends a new ECC that is correct for the data. Reading the new
block would result in a MEDIUM ERROR - Reallocated Uncorrectable Data
Read, with the sense key set to three and the sense code to AAH. Any
write to the new block will clear this condition. When RUEE is set to
zero and the drive determines that a hard error is encountered is
uncorrectable, the drive will not attempt automatic reallocation. A
CHECK CONDITION status, with a sense key of MEDIUM ERROR -
Uncorrectable Data Error will result. The default is zero.
FDPE - Fill Data Pattern Enabled (Byte 2, Bit 3)
------------------------------------------------
When FDPE is set to one, the drive will write the data pattern
specified in byte 2 of the FORMAT UNIT command into every user-
accesible sector on the drive when it exectes a FORMAT UNIT command.
When FDPE is set to zero, the drive will ignore the information in
byte 2 for the FORMAT UNIT command. Issuing a FORMAT UNIT command
typically causes loss of data, even if FDPE is set to zero. Users
should back up their data prior to formatting. The default is zero.
R - RESERVED
------------
Bit 2 of byte 2 is reserved and must be set to zero.
DUA - Disable Unit Attention
----------------------------
When DUA is set to one, the drive will not issue a CHECK CONDITION
status with the UNIT ATTENTION sense key on the first command follow-
ing a reset. The drive will execute the first command issued after a
reset condition. When DUA is set to zero, a UNIT ATTENTION condition
will exist following a power on, or a reset caused by either a BUS
DEVICE RESET message or a hard RESET condition. The default is zero.
DRT - Disable Reselection Timeout (Byte 2, Bit 0)
-------------------------------------------------
When DRT is set to one, the drive will not time out during a
reselection request. When DRT is set to zero and there is no BSY
response from the initiator after a selection time-out period - 250
milliseconds - the drive will clear the bus. The default is zero.
DDIS - Disable Disconnection (Byte 3, Bit 7)
--------------------------------------------
Setting DDIS to on eprevents disconnection and reconnection during
data transfer - either a read or write. The initial disconnection
due to the implied seek during the execution of a READ command is
not prevented, but no other disconnect will occur. On a WRITE
command, the drive will disconnect after transfetting all data to
the buffer. When DDIS is set to zero, disconnection is not
suppressed. The default is zero.
DELDIS - Delay of Disconnection (Byte 3, Bit 6)
-----------------------------------------------
This parameter is neither used nor required by applications using the
drive. It is ignored. The default is zero.
R - RESERVED
------------
Bit 5 of byte 3 is reserved and must be set to zero.
DPC - Disable Parity Control (Byte 3, Bit 4)
--------------------------------------------
When set to zero, DPC controls parity checking of data across the
SCSI bus. Setting DPC to one disables parity checking (the drive
still generates parity, but does not perform parity checking). The
default is zero.
SSID - Software Selectable ID (Byte 3, Bit 3)
---------------------------------------------
When SSID is set to zero, the jumper settings on the drive PCB
determine the drive's SCSI ID at all times. When SSID is set to one,
the SCSIADR bits (bits 0-2 of byte 3) determine the drive's SCSI ID
and the jumper settings will be ignored. When the SSID bit is set to
one, the SCSI ID will remain unchanged until the next reset or power
power on. If at initial power on, the SSID bit is set to one - that
is, if this bit's previous setting was saved on the disk - the
SCSIADR bits will determine the drive's SCSI ID. Otherwise, the
jumper settings on the drive PCB will determine its SCSI ID. The
default is zero.
SCSIADR - SCSI Address (Byte 3, Bits 2-0)
-----------------------------------------
If SSID (Bit 3 of byte 3) is set to one, SCSIADR determines the
drive's SCSI ID. If SSID is set to zero, the jumper settings on the
drive PCB determine its SCSI ID. The description of SSID above. The
default is zero.
PODIS - Product Option Jumper Enable (Byte 4, Bit 7)
----------------------------------------------------
When PODIS is set to one, the PO jumper on the drive is allowed to
control the drive fnctions specified by various bits in this byte
(byte 4) of Mode Page 39h. When PODIS is set to zero, the PO jumper
has no control over the drive functions specified in this byte. The
default is one.
POSS - Product Option Jumper Self-Seek Control (Byte 4, Bit 6)
--------------------------------------------------------------
When POSS is set to one, the PODIS bit is set to one, the SS bit in
this byte is set to one, and the PO jumper is installed, the drive
performs self-seek. If either POSS or PODIS are set to zero or the SS
bit is set to zero, or the PO jumper is not installed, the drive does
not perform self-seek. The default is zero.
POEP - Product Option Enable Parity Control (Byte 4, Bit 5)
-----------------------------------------------------------
When POEP is set to one, the PODIS bit is set to one, the DPC bit is
set to zero, and the PO jumper is installed, the drive performs
parity checking across the SCSI bus. If POEP or PODIS are set to
zero, or if the DPC bit is set to one or the PO jumper is not
installed, the drive continues to generate parity information, but
does not perform parity checking. The default is one.
POWS - Product Option Jumper Wait Spin Control (Byte 4, Bit 4)
--------------------------------------------------------------
When POWS is set to one, the POWS is set to one, the PODIS bit is set
to one, the WS bit is set to one, and the PO jumper is installed, the
drive performs Wait/Spins. If POWS or PODIS are set to zero, or if
the WS bit is set to zero or the PO jumper is not installed, the
drive does not perform Wait/Spin. The default is zero.
MTDLY - Motor Delay Soft Jumper (Byte 4, Bit 3)
-----------------------------------------------
When MTDLY is set to one, the drive delays the motor start by the
amount specified in the MOTOR DELAY TIME byte of this mode page. When
the bit is set to zero, no motor delay is implemented. The default is
zero.
SS - Self-Seek Soft Jumper (Byte 4, Bit 2)
------------------------------------------
Please refer to POSS description. The default is zero.
R - RESERVED
------------
Bit 1 of byte 4 is reserved and must be set to zero.
WS - Wait/Spin Soft Jumper (Byte 4, Bit 0)
------------------------------------------
Please refer to POWS description. The default is zero.
Motor Delay Time - (Byte 5)
---------------------------
The value stored in this byte specifies the motor delay time in 10
millisecond increments. The LSB (bit 0) is equal to 10 milliseconds.
Install
QUANTUM PRODRIVE LPS 270/540S PRODUCT MANUAL 81-104075-01 AUG. 1993
Notes on Installation
=====================
Installation direction
----------------------
horizontally vertically
+-----------------+ +--+ +--+
| | | +-----+ +-----+ |
| | | | | | | |
+-+-----------------+-+ | | | | | |
+---------------------+ | | | | | |
| | | | | |
| | | | | |
+---------------------+ | +-----+ +-----+ |
+-+-----------------+-+ +--+ +--+
| |
| |
+-----------------+
Orientation
-----------
The mounting holes on the ProDrive LPS 270/540S hard disk drive allow
the drive to be mounted in any orientation.
Mounting
--------
For mounting, #6-32 UNC screws are recommended.
CAUTION: The PCB is very close to the mounting holes. Do not exceed
the specified length for the mounting screws. The specified screw
length allows full use of the mounting-hole threads, while avoiding
damaging or placing unwanted stress on the PCB. To avoid stripping
the mounting-hole threads, the maximum torque applied to the screws
must not exceed 8 inch-pounds.
Clearance
---------
Clearance from the drive - except mounting surfaces - to any other
surface must be 0.05 inches minimum.
Ventilation
-----------
The LPS 270/540S hard disk drive operates without a cooling fan,
provided the ambient air temperature does not exceed 131*F (55*C).
Power Sequencing ---------------- You may apply the power in any order or manner, or short or open either the power or power-return line with no loss of data or damage to the disk drive. However, data may be lost in the sector being written at the time of power loss. The drive can withstand transient voltages of +10% to -100% from nominal while powering up or down.
Disk Caching
------------
The ProDrive LPS 270/540S hard disk drive incorporates DisCache
a 96K disk cache, to enhance drive performance. This integrated
feature can significantly improve system throughput. Read and write
caching can be enabled or disabled using the SET CONFIGURATION
command.
Acoustics --------- +-----------------+-----------------------+----------+ | Operating Mode | Measured Noise | Distance | +-----------------+-----------------------+----------+ | Idle On Track | 33 dBA pressure level | 1 m | | typical | 4.0 Bels (sound power)| 39.3 in. | +-----------------+-----------------------+----------+ | Idle On Track | 36 dBA pressure level | 39.3 in | | maximum | 4.2 Bels (sound power)| (1 m) | +-----------------+-----------------------+----------+
Automatic Actuator Lock
-----------------------
To ensure data integrity and prevent damage during shipment, the
drive uses a dedicated landing zone and Quantum's patented AIRLOCK.
The AIRLOCK holds the headstack in the landing zone whenever the
disks are not rotating. It consists of an air vane mounted near the
perimeter of the disk stack and a locking arm that restrains the
actuator arm assembly.
When DC power is applied to the motor and the disk stack rotates, the
rotation generates an airflow on the surface of the disk. As the flow
of air across the air vane increases with disk rotation, the locking
arm pivots away from the actuator arm, enabling the headstack to move
out of the landing. When DC power is removed from the motor, an
electric return mechanism automatically pulls the actuator into the
landing zone, where the AIRLOCK holds it in place.
Connectors
----------
J1 is a two section combination connector. The drive's DC power is
applied to section A. The SCSI interface (50-pin) uses section B. The
connector is mounted on the back edge of the printed-circuit (PCB).
+----------------------------------------+
| |
| |
| +-----J1--Section-B----------Section-A |
| |+-------------------------++4-3-2-1+| |
| ||oooooooooooooooooooooooo1||O O O O|| |
| ||ooooooooooooooooooooooooo|| || |
| |+-------------------------++-------+| |
+-+------------------------------------+-+
Recommended header connector and strain relief:
50-pin connector base part AMP P/N 1-746195-2 or equivalent 50-pin connector strain relief AMP P/N 499508-2 or equivalent
Recommended mating connector and their part numbers:
4-pin connector (J11 section A) AMP P/N 1-480424-0 or equivalent
Loose-piece contacts AMP P/N VS 60619-4 or equivalent
Strip contacts AMP P/N VS 61117-4 or equivalent
-------------------+ --+ +------------+| pin 1 +12 VDC 1| | 4 3 2 1 || pin 2 +12 Volts Return -+ +------------+| pin 3 + 5 Volts Return ------------------+ pin 4 + 5 VDC
LED Connector (J2) ------------------ The LED connector my be used to connect an external LED for the pur- pose of monitoring drive activity. A 220-ohm resistor is connected in series from the +LED pin to +5 volts. The -LED pin is connected to a switching transistor on the drive that turns on and lights the LED when the disk is performing a read or write operation. When no read or write operation is taking place, the transistor turns off and the LED is extinguished.
+---------------------+--------------------------------+ | J2 Pins | Mating Connectir Type and Part | |Pin Number| Function | Number (or equivalent) | +----------+----------+--------------------------------+ | 1 | -LED | Two-position housing: | +----------+----------+ Molex P/N 51021-0200 | | 2 | +LED | Loose-piece contacts: | | | | Molex P/N 50058-8100 | +----------+----------+--------------------------------+
J5 Control Connector -------------------- J5 may be used to connect an external switch for setting the SCSI ID of the drive. The recommended mating connectors are: +---+-------------+----------------------------+ |Pin|Function | Mating Connector Type and | | | | Part Number (or equivalent)| +---+-------------+----------------------------+ | 1 |Ground | Five position housing: | | 2 |A2 | Molex P/N 51021-0500 | | 3 |A1 | Loose-piece contacts: | | 4 |A0 | Molex P/N 50058-8100 | | 5 |RESERVED (no | | | |connection) | | +---+-------------+----------------------------+
DC Motor Assembly
-----------------
Integral with the base casting, the DC motor assembly is a fixed-
shaft, brushless DC spindle motor that drives the counter-clockwise
rotation of the disks.
Air Filtration
--------------
The ProDrive LPS hard disk drives are Winchester-type drives. The
heads fly very close to the media surface. Therefore, it is essential
that the air circulating within the drive be kept free of particles.
Quantum assembles the drive in a Class-100, purified air environment,
then seals the drive with a metal cover. When the drive is in use,
the rotation of the disks forces the air inside of the drive through
an internal filter.
Features
QUANTUM PRODRIVE LPS 270/540S PRODUCT MANUAL 81-104075-01 AUG. 1993
Product Overview
----------------
Quantum's ProDrive LPS 270/540S hard disk drives are a part of a
family of high-performance, 1-inch-high, hard disk drives
manufactured to meet the highest product quality standards. ProDrive
LPS hard disk drives use nonremovable, 3 -inch hard disks.
The ProDrive LPS 270/540S hard disk drives feature an embedded SCSI
drive controller and use SCSI commands to optimize system
performance. Because the drive manages media defects and error
recovery internally, these operations are fully transparent to the
user.
The innovative design of ProDrive LPS 270/540S hard disk drives
enables Quantum to produce a family of low-cost, high-reliability
drives.
Performance:
Average rotational latency of 6.7 ms
128K buffer with 96K dynamic segmentation cache. Look-ahead DisCache
feature with continues prefetch and WriteCache write-buffering
capabilities.
Read-on-arrival
ECC-on-the-fly
1:1 interleave on read/write operations
SCSI-bus active termination
SCSI-bus active negation drivers
Formatted Capacity
------------------
At the factory, the ProDrive LPS 270/540S receives a low-level
format that creates the actual tracks and sectors on the drive.
Reliability
-----------
Mean Time Between Failures (MTBF):
150,000 Power On Hours (POH), typical usage
The Quantum MTBF numbers represent Bell-Core MTBF TR-TSY-000332
predictions and represent the minimum MTBF that Quantum or a customer
would expect from the drive. The projected field MTBF is 300,000
hours.
Preventive Maintenance (PM):
Not required
Start/Stop:
20,000 cycles (minimum)
Component Life:
5 Years
Error Detection and Correction
------------------------------
As disk drive areal densities increase, obtaining extremely low error
rates requires a new generation of sophisticated error-correction
codes. Quantum ProDrive LPS 270/540S series hard disk drives
implement 112-bit single and double burst Reed-Solomon error-
correction techniques to reduce the uncorrectable read error rate to
less than one bit in 1 x 10(14) bits read.
When errors occurs, an automatic retry and a more rigorous double-
burst correction algorithm enable the correction of any sector with
two bursts of three incorrect bytes each or up to six multiple
random one-byte burst errors. In addition to these advanced error
correction capabilities, the drive's additional cross-checking code
and algorithm double checks the main ECC correction to greatly re-
duce the probability of miscorrection.
Defect Management
-----------------
The ProDrive LPS 270/540S allocates one sector per two tracks as a
spare. In the factory, the media is scanned for defects. If a sector
on a cylinder is found to be defective, the address of the sector is
added to the drive's defect list. Sectors located physically
subsequent to the defective sector are assigned logical block
addresses such that a sequential ordering of logical blocks results.
This inline sparing technique is employed in an attempt to eliminate
slow data transfer that would result from a single defective sector
on a cylinder in a ProDrive LPS 270S hard disk drive and two
defective sectors on a cylinder in a ProDrive LPS 540S hard disk
drive.
If more than one sector is found defective on a cylinder, the inline
sparing technique is applied only to the first sector. The remaining
defective sectors are replaced with the nearest available spare
sectors on nearby cylinders. Such an assignment of additional
replacement sectors from nearby sectors rather than having a central
pool of spare sectors is an attempt to minimize the motion of the
actuator and head that otherwise would be needed to find a replace-
ment sector. The result is minimal reduction of data throughput.
Seek Time
---------
+----------------------------------+--------+
| |270/540S|
+----------------------------------+--------+
|Track-to-Track msec. typ. | 4 |
+----------------------------------+--------+
|Average write msec. typ. | 13 |
| msec. max. | 14 |
+----------------------------------+--------+
|Full stroke msec. typ. | 23 |
| msec. max. | 25 |
+----------------------------------+--------+
Data Transfer Rates
-------------------
Data is transferred from the disk to the read buffer at a rate up to
5.8 MB/s in bursts. Data is transferred from the read buffer to the
SCSI bus at a rate of up to 6.0 MB/sec in the asynchronous mode, or
at up to 10.0 MB/s in the synchronous mode.
Track and Cylinder Skewing
--------------------------
Track and cylinder skewing in the ProDrive LPS 270/540S minimizes
latency time and thus increases data throughput.
Track Skewing
-------------
Track skewing reduces the latency time that results when the drive
must switch read/write heads to access sequential data. A track skew
is employed such that the next logical sector of data to be accessed
will be under the read/write head once the head switch is made and
the data is ready to be accessed. Thus, when sequential data is on
the same cylinder but on a different disk surface, a head switch is
needed but not a seek. Since the sequential head-switch time is well
defined on the ProDrive LPS 270/540S, the sector addresses can be
optimally positioned across track boundaries to minimize the latency
time during a head switch.
Cylinder Skewing
----------------
Cylinder Skewing also is used to minimize the latency tome associated
with a single-cylinder seek. The next logical sector of data that
crosses a cylinder boundary is positioned on the drive such that
after a single-cylinder seek is performed, and when the drive is
ready to continue accessing data, the sector to be accessed is
positioned directly under the read/write head. Therefore, the
cylinder skew takes place between the last sector of data on the last
head of a cylinder and the first sector of data on the first head of
the next cylinder. Since single-cylinder seeks are well defined on
the ProDrive LPS 270/540S, the sector addresses can be optimally
positioned across cylinder boundaries to minimize the latency time
associate with a single-cylinder seek.
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