Read-Ahead Cache; Data Buffer Configuration - Fujitsu MPG3XXXAH Product Manual

6.5

Read-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.
6.5.1

Data buffer configuration

The device has a 2MB 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).
for MPU work
80 KB
(81,920 bytes)
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.
2,048 KB (2,097,152 bytes)
For R/W command
1,968 KB
(2,015,232 bytes)
Figure 6.9 Data buffer configuration
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