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C141-E205 1-3
Note:
The maximum data transfer rate in asynchronous mode may be limited by the response time of
initiator and the length of SCSI bus length. The maximum data transfer rate in synchronous
mode may be limited by the cable length, transmission characteristics of the SCSI bus and the
connected SCSI device number.
(5) Continuous block processing
The addressing method of data blocks is logical block address. The initiator can access data by
specifying block number in a logically continuous data space without concerning the physical
structure of the track or cylinder boundaries.
The continuous processing up to [64K-1] blocks in a command can be achieved, and IDD can perform
continuous read/write operation when processing data blocks on several tracks or cylinder.
(6) Programmable multi-segment data buffer
The data buffer is 8M bytes. Data is transferred between SCSI bus and disk media through this
data buffer. This feature provides the suitable usage environment for users.
Since the initiator can control the disconnect/reconnect timing on the SCSI bus by specifying the
condition of stored data to the data buffer or empty condition of the data buffer, the initiator can
perform the effective input/output operations with utilizing high data transfer capability of the
SCSI bus regardless of actual data transfer rate of the disk drive.
(7) Cache feature
After executing the READ command, the IDD reads automatically and stores (prefetches) the
subsequent data blocks into the data buffer (Read-ahead caching).
The high speed sequential data access can be achieved by transferring the data from the data buffer
without reaccessing the disk in case the subsequent command requests the prefetched data blocks.
The write cache feature is supported. When this feature is enabled, the status report is issued without
waiting for completion of write processing to disk media, thereby enabling high speed write processing.
IMPORTANT
When Write cache is enabled, you should ensure that the cashed
data is surely flushed to the disc media before you turn off the drive's
power.
To ensure it, you should issue either the SYNCHRONIZE CASHE
command or the STOP UNIT command with specifying “0” to the
Immediate bit and then confirm that the command is surely
terminated with the GOOD STATUS.