Product manual

Barracuda 2LP Product Manual, Rev. D 17
and cleared, if needed, for any logical blocks that are being written (see the
SCSI-2 Interface Product Manual ).
If the number of write data logical blocks exceeds the size of the segment
being written into when the end of the segment is reached, data is written
into the beginning of the same cache segment, overwriting data that was
written there at the beginning of the operation. However, the drive does not
overwrite data that has not yet been written to the disc.
5.7 Synchronized spindle operation
The synchronized spindle operation allows several drives operating from the
same host to operate their spindles at the same synchronized rotational rate.
Drives operating in a system in synchronized mode increase the system’s
capacity and transfer rate in a cost-effective manner.
The interface consists of a twisted-pair cable, which connects the drives in
the synchronized system in a daisy-chain configuration as shown below.
Master Sync
Source
Host
(or other drive)
Spindle
Control
Drive 1
+5V
R
T
Spindle
Control
Drive 2
+5V
R
T
Spindle
Control
Drive n
+5V
R
T
Sync Interface
System
Interface
J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives
J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives
J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives
J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives
J4 Pin 1 on N/ND drives
J4 Pin 6 on WC/DC drives (+SSREF)
J5 Pin 11 on W/WD drives
J4 Pin 2 on N/ND drives
J5 Pin 12 on W/WD drives
Figure 4. Synchronized drive interconnect diagram
The host can reconfigure the drive any time after power-up to be the master
or a slave by using the Mode Select command on the Rigid Disc Drive
Geometry page. The master provides the reference signal to which all other
drives phase-lock, including the master. There is only one master per
system, and that can be a drive or the host computer. All drives may be
configured as slaves allowing the host to provide the reference signal.
Each drive also can be configured for the non-synchronized mode in which
it ignores any reference signal that might be present—this is the default mode
as shipped from the factory. Connect the synchronized reference signal to
the host only if the host provides the reference signal. If the host does not
provide the reference signal, do not connect the host.