Seagate Ultra160 Product Manual page 221

SCSI Interface Product Manual, Rev. B
[6] When the Disable Force Unit Access (DFUA) bit is set to 1, the drive ignores the FUA bit in read and write
commands. This can result in better drive performance in some circumstances. When the DFUA is set to
0, the drive obeys the FUA setting in read and write commands.
[7] When the ROUND bit equals one, the drive treats and reports rounded parameters as described in Sec-
tion 7.8. When ROUND equals zero, the drive shall round the parameter and handle command completion
reporting as if the parameter had not been rounded.
[8] When the STRICT bit is a one, the drive checks for initiator attempts to change unchangeable parameters.
If the drive detects an attempt, it rejects the command in the standard way, i.e., CHECK CONDITION sta-
tus from drive, REQUEST SENSE from the initiator, and ILLEGAL REQUEST sense key (5h) back from
the drive. When the STRICT bit is zero, the drive ignores the values of the unchangeable parameters in a
MODE SELECT command. The drive does not reject the command trying to change unchangeable
parameters.
[9] When set to one, the SCSI-2 bit changes the following SCSI-3 features from their SCSI-3 definition to the
SCSI-2 definition. When S2 equals zero, the following features remain as specified in other portions of this
specification:
a. Control Mode Page (0Ah) Length from 0Ah to 06h.
b. Caching Page (08h) Length from 12h to 0Ah.
[10] These bits are reserved for future compatibility with Seagate host adapters. Though they presently may be
changeable, (see note [9]) these bits do not control anything, unless the individual drive's Product Manual,
Volume 1, indicates that they do and defines their use in the MODE SENSE Data section.
[11] See individual drive's Product Manual, Volume 1, MODE SENSE Data section for a table showing codes
that indicate which of these bits are changeable by the host using the MODE SELECT command.
[12] A Parameter Savable (PS) bit of one indicates that the drive is capable of saving the page in a nonvolatile
vendor-specific location (used only with MODE SENSE command).
[13] If the Self SEEK bit is set to one, the drive will enter self seek mode for testing purposes. Such testing
could include, but is not limited to, power dissipation and acoustics. While in this mode, the drive will
accept SCSI commands and will process them in between the self seek operations, including a mode
select to turn this bit back off. As such, this bit should be off for normal drive operations. If this bit is set to
zero, the drive will not self seek; normal operating mode.
[14] The four JIT (Just In Time) bits allow you to enable and disable certain seek speeds. JIT0 represents the
fastest seek type used by the drive, JIT1 represents the second fastest, JIT2 represents the third fastest,
and JIT3 represents the slowest seek type. You can use these bits to reduce accoustics by disabling the
fastest seeks. This can also reduce power consumption (from seek activity). These JIT settings only affect
user read and write operations. Background drive operations and user seek commands will always use
the fastest seek type. When the bit is set to 1, the drive is allowed to use this seek type in its seek speed
algorithm. When the bit is set to 0, the drive is not allowed to use this seek type in its seek speed algo-
rithm. If all JIT bits are set to zero, the drive enables JIT0 only. If all bits are set to one, the drive firmware
selects the slowest (quietest) seek speed that does not hurt performance.
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