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1.1 Features
C156-E205-01EN 1-5
(3) Data buffer
7,600 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
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.