6.5 Read-Ahead Cache
C141-E057-01EN
6-15
•
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.
1)
Read-ahead data read from the medium to the data buffer after completion of
the command that are object of caching operation.
2)
Data transferred to the host system once by requesting with the command that
are object of caching operation (except for the cache invalid data by some
reasons).
3)
Remaining data in the data buffer (for write command) transferred from the
host system by the command that writes data onto the disk medium, such as
the WRITE SECTOR (S), WRITE DMA, WRITE MULTIPLE.
Followings are definition of in case that the write data is treated as a cache data.
However, since the hit check at issurance of read command is performed to the
data buffer for read command prioritily, caching write data is limited to the case
that the hit check is missed at the data buffer for read command.
•
When all data requested by the read command are stored in the data buffer for
write command (hit all), the device transfers data from the data buffer for
write command. At this time, the read-ahead operation to the data subsequent
to the requested data is not performed.
•
Even if a part of data requested by the read command are stored in the data
buffer for write command (hit partially), all data are read from the disk
medium without transferring from the data buffer for write command.
(3) Invalidating caching data
Caching data in the data buffer is invalidated in the following case.
1)
Following command is issued to the same data block as caching data.
−
WRITE SECTOR(S)
−
WRITE DMA
−
WRITE MULTIPLE
2)
Command other than following commands is issued (all caching data are
invalidated)
−
READ SECTOR (S)
−
READ DMA
Summary of Contents for MHE2043AT
Page 1: ...C141 E057 02EN MHE2064AT MHE2043AT MHF2043AT MHF2021AT DISK DRIVE PRODUCT MANUAL ...
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Page 42: ...3 1 Dimensions C141 E057 01EN 3 3 Figure 3 1 Dimensions MHF series 2 2 ...
Page 52: ...3 4 Jumper Settings C141 E057 01EN 3 13 Figure 3 14 Example 2 of Cable Select ...
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Page 58: ...4 3 Circuit Configuration C141 E057 01EN 4 5 Figure 4 2 Circuit Configuration 16 bit ...
Page 64: ...4 6 Read write Circuit C141 E057 01EN 4 11 Figure 4 4 Read write circuit block diagram ...
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Page 171: ...Interface 5 96 C141 E057 01EN Figure 5 10 Data transfer timing ...
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