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The drive is low-level formatted at the factory. You cannot low-level
format the drive.
ST3390AST3550AST3655A
Formatted capacity (Mbytes*)341.311452.415528.482
Total sectors666,624883,6241,032,192
* One megabyte equals one million bytes.
1.1.1Recommended logical configuration
You can operate the drive using many different logical configurations,
provided the number of sectors per track does not exceed 256. However,
in DOS the number of sectors per track must be less than or equal to 63.
When establishing the logical configuration, set the number of sectors
per track and the number of heads to satisfy the following relationship:
16
≤
(sectors per track)(heads) ≤ 4,096
When you configure the drive in CMOS, the total sectors cannot exceed
the physical capacity of the drive. The total sectors is determined by the
following formula:
total sectors = (logical heads) (logical sectors per track) (logical cylinders)
To maximize the capacity of the drive, the following geometry is recom-
mended:
ST3390AST3550AST3655A
Cylinders7681,0181,024
Read/write heads141416
Sectors per track626263
The drive is configured in translation mode. You can verify the number
of cylinders, sectors per track and heads by using the Identify Drive (EC
command. See Section 3.1.1 for details about the Identify Drive command.
H
)
2ST3655 Family AT Drives Product Manual, Rev. A
1.1.2Physical organization
ST3390AST3550AST3655A
Read/write heads355
Servo heads111
Discs233
1.2Functional specifications
InterfaceAT
Zone Bit Recording methodRLL (1,7)
External data burst transfer rate
(Mbytes per sec)
Internal data transfer rate
(Mbits per sec)
Spindle speed (RPM)4,500 ± 0.5%
Cache size (Kbytes)256
Bytes per sector512
Recording density, max (BPI)53,192**
Track density (TPI)3,000**
* The drives achieve this external transfer rate when using programmed
I/O with IORDY, as shown in Figure 11 on page 32.
** The ST3550A has a recording density of 52,602 bits per inch and a
track density of 2,400 tracks per inch.
11.1*
21.6 to 36.56
1.3Seek time
Seek time is a true statistical average of at least 5,000 measurements of
seek time. All measurements are under nominal conditions of temperature and voltage with the drive mounted horizontally. The specifications
in the table below are defined as follows:
• Track-to-track seek time is the average of all possible single-track
seeks in both directions.
• Average seek time is measured by executing seeks in both directions
between random cylinders.
• Full-stroke seek time is half the time needed to seek from track 0 to
the maximum track and back to track 0.
ST3655 Family AT Drives Product Manual, Rev. A3
Track-to-track
seek time
3.5 msec typ
4.0 msec max
Note. Host overhead varies between systems and cannot be specified.
Drive internal overhead is measured by issuing a no-motion seek.
Overhead is typically less than 0.5 msec.
Average
seek time
12.0 msec typ
14.0 msec max
Full-stroke seek
time
30.0 msec typ
32.0 msec max
Average
latency
6.67 msec
1.3.1Thermal compensation
The thermal compensation feature compensates for position offset of the
selected head because of variations in temperature. The drive automatically compensates for thermal offset every 30 seconds for the first 30
minutes of operation and every 1.5 minutes thereafter. The drive performs this automatic compensation while executing a command from the
computer.
You can pre-empt the automatic compensation by issuing a Recalibrate
command. The drive performs a thermal compensation, sets a timer and
waits 2 minutes before performing the automatic compensation again.
Thermal compensation increases the execution time of the command
during which it is performed by 100 msec (typ) to 350 msec (max).
1.3.2Multisegmented cache buffer
The drive uses the cache buffer to improve performance by eliminating
access times under certain conditions. The cache buffer contains four
64-Kbyte segments of RAM (one for writing and three for reading) for a
total capacity of 256 Kbytes.
Read look-ahead. The drive uses the read segments to store additional
logical sectors, after the last requested sector, into a buffer before the
additional sectors are requested by the computer. The cache buffer
stores data from the start of a read until the buffer segment is full, or until
another command is received from the computer.
Write immediate. The drive uses the write segment to store write
commands and data. After the drive receives all the data for the command, it issues a write complete. Then, the drive writes the data to the
disc.
Write merging. The drive accepts contiguous write commands and
executes them as one command.
4ST3655 Family AT Drives Product Manual, Rev. A
1.4Start/stop time
Within 20 seconds after DC power is applied, the drive is ready. Within
15 seconds after DC power is removed, the drive spindle stops rotating.
1.5Typical power-up and power-down sequence
The typical power-up and power-down sequences assist you in evaluating the drive’s performance; they are not performance specifications.
1.5.1Power-up sequence
1. Power is applied to the drive.
2. When power is applied, the LED is on for about 1 second.
3. The spindle motor reaches operating speed in about 4 seconds.
4. The arm-lock solenoid releases the arm, making an audible sound.
5. The drive performs velocity adjustment seeks.
6. The heads are positioned ov er track 0 and the drive is ready.
1.5.2Power-down sequence
Caution. Do not move the drive until the motor has come to a complete
stop.
1. The power is turned off.
2. Within 3 seconds, the motor begins to spin down.
3. The read/write heads automatically move to the shipping zone, which
is inside the maximum data cylinder.
4. The arm-lock solenoid locks the arm, making an audible sound. This
completes the power-down sequence.
1.5.3Auto-park
Upon power-down, the read/write heads automatically move to the
shipping zone. The heads park inside the maximum data cylinder and
the arm-lock solenoid engages, making an audible sound. When power
is applied, the heads recalibrate to track 0.
ST3655 Family AT Drives Product Manual, Rev. A5
1.6Reliability
Read error rates are measured with automatic retries and data correction
with ECC enabled and all flaws re-allocated. The mean time between
failures (MTBF) is measured at nominal power at sea level and an
ambient temperature of 40°C.
Nonrecoverable read errors1 per 10
Seek errors1 per 10
MTBF250,000 power-on hours
Service life5 years
13
bits transferred
7
physical seeks
1.7Physical dimensions
The mounting dim ensions are shown in Figure 8 on page 24.
Height, max1.00 inch (25.4 mm)
Operating5°C to 55°C (41°F to 131°F)
Nonoperating–40°C to 65°C (–40°F to 149°F)
1.8.2Temperature gradient
Operating20°C per hour (36°F per hour)
Nonoperating30°C per hour (54°F per hour)
1.8.3Altitude
Operating–1,000 ft to 10,000 ft (–305 m to 3,048 m)
Nonoperating–1,000 ft to 40,000 ft (–305 m to 12,192 m)
6ST3655 Family AT Drives Product Manual, Rev. A
1.8.4Relative humidity
Operating8% to 80% noncondensing
Maximum wet bulb 26°C (79°F)
Maximum operating
gradient
Nonoperating5% to 95% noncondensing
10% per hour
Maximum wet bulb 26°C (79°F)
1.9Acoustics
Sound pressure is measured from 1 meter above the drive top cover at
idle.
Sound pressure, typ (dBA)34
Sound pressure, max (dBA)38
1.10 Shock and vibration
All shock and vibration specifications assume that the drive is mounted
in a recommended orientation (see Figure 7 on page 23) with the input
levels measured at the drive mounting screws. Shock measurements are
based on an 11 msec, half sine wave shock pulse, not to be repeated
more than twice per second.
During normal operating shock and vibration, there is no physical damage to the drive or performance degradation. During nonoperating shock
and vibration, the read/write heads are positioned in the shipping zone.
OperatingNonoperating
Shock2 Gs75 Gs
5–22 Hz vibration0.020-inch
displacement
22–500 Hz vibration0.50 Gs4.00 Gs
0.020-inch
displacement
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