Write Caching; Defect Management - Samsung WA31273A Technical Manual

Disk Drive Operation
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EXECUTE DRIVE DIAGNOSTIC (90h)
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READ LONG (23h)
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WRITE VERIFY (3Ch)
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INITIALIZE DEVICE PARAMETER (91h)
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SLEEP (99h, E6h)
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STANDBY IMMEDIATELY (94h,E0h)
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READ BUFFER (E4h)
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WRITE BUFFER (E8h)
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WRITE SAME (E9h)
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Write Caching

Write caching improves both single and multi-sector write performance by reducing delays introduced
by rotational latency. When the drive writes a pattern of multiple sequential data, it stores the data to a
cache buffer and immediately sends COMMAND COMPLETE message to the host before it writes the
data to the disk.
The data is then written collectively to the drive thereby minimizing the disk seeking operation. Data
is held in cache no longer than the maximum seek time plus rotational latency. Host retries must be
enabled for write cache to be active.
If the data request is random, the data of the previous command is written to the disk before
COMMAND COMPLETE is posted for the current command. Read commands work similarly. The
previous write is allowed to finish before the read operation starts.
If a defective sector is found during a write, that sector is automatically relocated before the write
occurs. This ensures that cached data that already has been reported as written successfully gets
written, even if an error should occur.
If the sector is not automatically relocated, the drive drops out of write caching and report the error as
an ID Not Found. If the write command is still active on the AT interface, the error is reported during
that command. Otherwise, it is reported on the next command.
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Defect Management

The Winner 3A WA31273A / WA32543A / WA33203A / WA32163A / WA31083A, Winner 2A
WA32162A media is scanned for defects as part of the factory test process. After the defect scanning
the defective sectors are saved in the defect list. The defect encountered in manufacturing process is
slipped to next physical sector location. All logical sector numbers are pushed down to maintain
sequential order of data. The read/write operation can "slip" over the defective sectors and
performance impact is idle time during defective sectors only.
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16 WA31273A / WA32543A / WA33203A / WA32163A / WA31083A /