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C156-E142-02EN 1 - 5
(3) Data buffer
1,844 KB buffer is used to transfer data between the EIDE bus and disk. Since data is stored in
this buffer, the host can execute input-output processing effectively by using the high-speed data
transfer capability of the EIDE bus without regard to the data transfer rate of the optical disk drive.
(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 data
is transferred from the buffer without another disk access.
(5) Write cache feature
When the host system issues the write command to the optical disk drive, a command complete is
usually responded after completion of the write and verify operations. By using the write cache
feature, a command complete is responded after completion of the data transfer to the data buffer
without waiting the completion of the write and verify operations then the write and verify
operations are made asynchronously with the interface operation. Therefore, the apparent write
command processing time measured at the host system is reduced and the I/O performance of the
host system is improved.
The write cache feature is enabled or disabled by MODE SELECT command.
When the write cache feature is enabled, a write error is reported at the
completion status of next command. At a system so that the host retries
the command, a retry process may be failed.
(6) Defective block slipping
When a disk is initialized, logical data blocks are reallocated in a physical sequence by slipping
defective data blocks. This enables high-speed continuous data block processing without
rotational delay due to defective data blocks.
(7) Device driver software (1.3 GB optical disk media)
The optical disk drive requires more extended processing time than conventional optical device
drives because of higher density. Consequently, a processing time timeout when using the OS can
occur and this requires special device driver software.