Seek Overlap; Write Cache Function - Hitachi 7K320 - Travelstar Mobile Hard Drive Specifications

Figure 8 Set Max security mode transition
12.11

Seek Overlap

HTS7232XXL9SAXX / HTS7232XXL9A3XX provide accurate seek time measurement method. The
seek command is usually used to measure the device seek time by accumulating execution time for a
number of seek commands. With typical implementation of the seek command, this measurement
must including the device and host command overhead. To eliminate this overhead,
HTS7232XXL9SAXX / HTS7232XXL9A3XX overlap the seek command as described below.
The first seek command completes before the actual seek operation is over. Then device can receive
the next seek command from the host but actual seek operation for the next seek command starts
right after the actual seek operation for the first seek command is completed. In other words, the
execution of two seek commands overlaps excluding the actual seek operation.
With this overlap, total elapsed time for a number of seek commands is the total accumulated time
for the actual seek operation plus one pre and post overhead. When the number of seeks is large, just
this one overhead can be ignored.
Figure 9 Seek overlap
12.12

Write Cache Function

Write cache is a performance enhancement whereby the device reports completion of the write
command (Write Sector(s) and Write Multiple) to the host as soon as the device has received all of
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7K320 SATA OEM Specification