Read-Ahead Cache; Data Buffer Structure; Figure 6.7 Data Buffer Structure - Fujitsu MHT2080AH - 80GB 5400 RPM PATA Hard Drive Product Manual

Operations

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 8 MB. 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 Figures 6.7 and 6.8.)
For MPU work
304 KB
The read-ahead operation is done by the following commands.
READ SECTOR (s) (EXT)
READ MULTIPLE (EXT)
READ DMA (EXT)
READ DMA QUEUED (EXT)
READ STREAM PIO
READ STREAM DMA
6-12
8192 KB (8388608 bytes)
For R/W command
7824 KB

Figure 6.7 Data buffer structure

For MPU work
64 KB
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