Seagate MEDALIST 1080SL Product Manual page 101

Medalist 1080sl SCSI Product Manual, August 1995
Byte 2 The initiator control (IC) bit is not supported.
When the abort prefetch (ABPF) bit is 0, the drive controls
completion of prefetch. See the description for the DISC bit,
below. This is the default value and it is not changeable.
The caching analysis permitted (CAP) bit is not supported.
When the discontinuity (DISC) bit is 1, the drive may prefetch
across cylinder boundaries, where head seeks consume addi-
tional processing time. This is the default value and it is not
changeable.
The size enable (SIZE) bit is not supported.
When the write cache enable (WCE) bit is 0, the drive returns a
good status for a Write command after successfully writing all
the data to the media. When the WCE bit is 1, the drive returns
a good status for a Write command after successfully receiving
the data and before writing it to the media.
When the multiplication factor (MF) bit is 0, the drive interprets
the minimum prefetch and maximum prefetch fields as the
number of logical blocks to be prefetched. When the MF bit is 1,
the drive interprets the minimum prefetch and maximum prefetch
fields in terms of a number which, when multiplied by the transfer
length of the current command, yields the number of logical
blocks to be prefetched.
When the read cache disable (RCD) bit is 0, the drive may return
data requested by a Read command by accessing either the
cache or the media. If the RCD bit is 1, the cache is not used.
Byte 3 The demand read retention priority field is not used. The
initiator cannot assign any special retention priority to the
drive.
The write retention priority field is not used. The initiator
cannot assign any special retention priority to the drive.
Bytes 4–5 The disable prefetch transfer length always has a value
of FFFF , which means that the drive attempts an antici-
H
patory prefetch for all Read commands.
The minimum prefetch field specifies the minimum num-
Bytes 6–7
ber of blocks the drive prefetches, regardless of the delays
it may cause in executing subsequent pending com-
mands. When the minimum prefetch field contains 0, the
drive terminates prefetching whenever another command
is ready to be executed. If the minimum prefetch equals
the maximum prefetch, the drive prefetches the same
number of blocks regardless of whether there are com-
mands pending.
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