Fujitsu MPD3XXXAT manual Read-Ahead Cache, 9 Data buffer configuration

6.5Read-Ahead Cache

After a read command which reads the data from the disk medium is completed, the read- ahead cache function reads the subsequent data blocks automatically and stores the data in the data buffer.

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 access the data at higher speed.

6.5.1Data buffer configuration

The device has a 512-KB data buffer. The buffer is used by divided into two and other commands parts; for MPU work, for read cache of read commands and other commands (see Figure 6.9).

		512 KB (524,288 bytes)
for MPU work			for R/W command
40.5 KB			471.5 KB (482,816 bytes)
(41,472 bytes)
	Figure 6.9 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 are stored in the buffer for read cache.

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