Fujitsu MHY2060BH 用户手册

 

6-14 

C141-E262 

The caching operation is performed only when the commands listed below are 
received.  If any of the following data are stored on the data buffer, the data is 
sent to the host system. 

• 

All of the sector data that this command processes. 

• 

A part of the sector data including the start sector, that this command 
processes. 

If part of the data to be processed is stored on the data buffer, the remaining data 
is read from disk media and sent to the host system. 

(1)  Commands that are targets of caching 

The commands that are targets of caching are as follows: 

• 

READ SECTOR (S) (EXT) 

• 

READ MULTIPLE (EXT) 

• 

READ DMA (EXT) 

• 

READ FP DMA QUEUED 

However, if the caching function is prohibited by the SET FEATURES command, 
the caching operation is not performed. 

(2)  Data that is a target of caching 

The data that is a target of caching are as follows: 

1)  Read-ahead data that is read from disk media and saved to the data buffer 

upon completion of execution of a command that is a target of caching. 

2)  Pre-read data that is read from disk media and saved to the data buffer before 

execution of a command that is a target of caching. 

3)  Data required by a command that is a target of caching and has been sent to 

the host system one. If the sector data requested by the host has not been 
completely stored in the read cache portion of the buffer, this data does not 
become a target of caching. Also, If sequential hits occur continuously, the 
caching-target data required by the host becomes invalid because that data is 
overwrited by new data.