Fujitsu MAP3147NC/NP, MAP3735NC/NP, MAP3367NC/NP manual

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.

CAUTION

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 and then confirm that the command is surely terminated with the GOOD STATUS.

(8)Command queuing feature

The IDD can queue maximum 128 commands, and optimizes the issuing order of queued commands by the reordering function. This feature realizes the high speed processing.

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