Table of Contents
Advertisement
ST3655 Family AT Drives Product Manual, Rev. A
Track-to-track
Average
seek time
seek time
3.5 msec typ
12.0 msec typ
4.0 msec max
14.0 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.
1.3.1 Thermal compensation
The thermal compensation feature compensates for position offset of the
selected head because of variations in temperature. The drive automat-
ically compensates for thermal offset every 30 seconds for the first 30
minutes of operation and every 1.5 minutes thereafter. The drive per-
forms 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).
1.3.2 Multisegmented 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 com-
mand, 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.
Full-stroke seek
Average
time
latency
30.0 msec typ
6.67 msec
32.0 msec max
3
Advertisement
Table of Contents
