Hitachi HTS541680J9AT00 Specifications - Page 80

Seek Overlap, Write Cache Function

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Travelstar 5K160 (PATA) Hard Disk Drive Specification 12.11 Seek Overlap HTS5416XXJ9AT00 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, HTS5416XXJ9AT00 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 37 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 the data into its buffer. The device assumes responsibility to write the data subsequently onto the disk. • While writing data after completed acknowledgment of a write command, soft reset or hard reset does not affect its operation. But power off terminates writing operation immediately and unwritten data are to be lost. • Flush cache, Soft reset, Standby, Standby Immediate and Sleep are executed after the completion of writing to disk media on enabling write cache function. So the host system can confirm the completion of write cache operation by issuing flush cache command, Soft reset, Standby command, Standby Immediate command or Sleep command, and then, by confirming its completion. 80/188

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Travelstar 5K160 (PATA) Hard Disk Drive Specification
80
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188
12.11
Seek Overlap
HTS5416XXJ9AT00 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, HTS5416XXJ9AT00 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 37 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 the data into its buffer. The device
assumes responsibility to write the data subsequently onto the disk.
•
While writing data after completed acknowledgment of a write command, soft reset or hard reset does not
affect its operation. But power off terminates writing operation immediately and unwritten data are to be
lost.
•
Flush cache, Soft reset, Standby, Standby Immediate and Sleep are executed after the completion of writing
to disk media on enabling write cache function. So the host system can confirm the completion of write
cache operation by issuing flush cache command, Soft reset, Standby command, Standby Immediate
command or Sleep command, and then, by confirming its completion.