Read-Ahead Cache; Data Buffer Structure; Figure 6.5 Data Buffer Structure - Fujitsu MJA2500BH - Mobile 500 GB Hard Drive Product/Maintenance Manual

6.4 Read-ahead Cache

Read-ahead Cache is the function for automatically reading data blocks upon
completion of the read command in order to read data from disk media and save
data block on a data buffer.
If a subsequent command requests reading of the read-ahead data, data on the data
buffer can be transferred without accessing the disk media. As the result, faster
data access becomes possible for the host.

6.4.1 Data buffer structure

This device contains a data buffer. This buffer is divided into two areas: one area
is used for MPU work, and the other is used as a read cache for another command.
(See Figure 6.5)
Example of 8 MB buffer
For MPU work
The read-ahead operation is done by the following commands.
•
READ SECTOR (S) (EXT)
•
READ MULTIPLE (EXT)
• READ DMA (EXT)
•
READ FP DMA QUEUED
C141-E293
8,192 KB (8,388,608 bytes)
For R/W command

Figure 6.5 Data buffer structure

6.4 Read-ahead Cache
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