Fujitsu MHN2300AT, MHN2150AT, MHN2100AT, MHN2200AT Data buffer configuration, Caching operation

Operations

When the next command requests to read the read-ahead data, the data can be transferred from the data buffer without accessing the disk medium. The host can thus access data at higher speed.

6.4.1 Data buffer configuration

The drive has a 2 MB data buffer. The buffer is used by divided into three parts; for read/write commands, and for MPU work (see Figure 6.9).

		2048 KB
for MPU works		for read/write commands
	80 KB		1968 KB

Figure 6.7 Data buffer configuration

The read-ahead operation is performed at execution of the READ SECTOR(S), READ MULTIPLE, or READ DMA command, and read-ahead data is stored in the buffer for read/write commands.

6.4.2 Caching operation

Caching operation is performed only at issuance of the following commands. The device transfers data from the data buffer to the host system at issuance of following command if following data exist in the data buffer.

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All sectors to be processed by the command

A part of data including load sector to be processed by the command

When a part of data to be processed exist in the data buffer, remaining data are read from the medium and are transferred to the host system.

(1) Commands that are object of caching operation

Follow commands are object of caching operation.

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READ SECTOR (S)

READ MULTIPLE

READ DMA

When caching operation is disabled by the SET FEATURES command, no caching operation is performed.

(2) Data that are object of caching operation

Follow data are object of caching operation.

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