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1.1 Features
C156-E228-02EN 1-5
(4) Read-ahead cache feature
The read-ahead cache feature enables high-speed sequential data access as
follows:
After executing a command to read data from the disk, the drive automatically
reads the next data block and stores it in the data buffer (pre-reading). If the next
command requests this data, the drive can transfer data from the buffer without
accessing the disk again.
(5) Write cache feature
When the host system issues the write command to the optical disk drive, this
drive would report completion of the command after completion of the write and
verify operations if the write cache feature were not used. If the write cache
feature is used, this drive reports completion of the command when data transfer
to buffer is completed, without waiting for completion of the write and verify
operations. This drive performs the write and verify operations asynchronously
with the interface operation. Therefore, enabling the write cache reduces the
apparent write command processing time recognized by the host system and
improves the I/O performance of the host system.
Enable or disable the write cache feature using the MODE SELECT command.
While the write cache feature is enabled, a write error is reported in
the completion status of another command that is subsequent to the
concerned write command. Note that, if the host performs only
retry of an error-reporting command, data in the block in which the
error has occurred is not correctly written.
(6) Defective block slipping
While initializing a disk, the optical disk drive slips defective data blocks to
reallocate logical data blocks so they are physically continuous. This enables
high-speed continuous data block processing without rotational delay due to
defective data blocks.