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SCSI-2 Drive Command Set

Mode Sense (Group 0) Command (1AH)

Chapter 2 2-61

SCSI-2 Drive Commands

RCD A Read Cache Disable bit of 1 indicates read ahead is

disabled.

A RCD bit of 0 indicates read ahead is enabled.

NOTE If WCE and RCD are both set to 1, a CHECK CONDITION status is

returned with the sense key/additional sense code set to ILLEGAL

REQUEST/Invalid Parameter List.

DisablePre-fetchTransfer

Length This field sets the threshold value for pre-fetching data

during reads. If the number of blocks to be read is

greater than this value, no pre-fetching occurs.

The Disable Pre-fetch Transfer Length default setting

is 64.

Minimum

Pre-fetch If this bit is set to 0 by the MODE SELECT command, a

CHECK CONDITION status is returned with the sense

key/additional sense code set to ILLEGAL REQUEST/

Invalid Parameter List. Since the MF bit is 1 and the

Minimum Pre-Fetch bit is also 1, the minimum pre-

fetch size is equal to the READ Transfer Length. This

field does not affect the operation of the drive.

The Minimum Pre-fetch default setting is 1 and cannot

be changed.

Maximum

Pre-fetch If this bit is set to 0 by the MODE SELECT command, a

CHECK CONDITION status is returned with the sense

key/additional sense code set tot ILLEGAL REQUEST/

Invalid Parameter List. Since the MF bit is 1 and the

Maximum Pre-fetch bit is also 1, the maximum pre-

fetch size is equal to the READ Transfer Length. This

field does not affect the operation of the drive.

The Maximum Pre-fetch default setting is 1 and cannot

be changed.

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HP 220mx Betriebsanweisung Seite 98