Product manual

When the Disable Read-Ahead (DRA) bit is 1, the drive
does not read into the buffer any logical blocks beyond
the addressed logical blocks. When the DRA bit equals 0,
the drive can continue reading logical blocks into the
buffer beyond the addressed logical blocks.
Byte 13 The
number of cache segments field determines how
many segments into which the cache should be divided.
Valid values are 1, 2, 4, 8, 16 and 32.
Bytes 14–15 The
cache segment size field indicates the segment size
in bytes. The cache segment size field is valid only when
the SIZE bit is 1.
Byte 16 Reserved.
Bytes 17–19 The
noncache segment size field always contains zeros.
This means that the entire buffer is available for caching.
ST3655 Family SCSI Drives Product Manual, Rev. A 105