Plextor
University - Data Transfer
Data Transfer Diagrams
CAV
(Constant Angular Velocity) Reading Method
CAV is a method where the speed of the spindle motor remains constant.
The read speed (green) increases to form a ramp like the one shown.
This ramp represents the constant increase in data throughput as the
laser moves closer to the outer edge of the disc. The motor RPM (orange)
remains the same.
Which drives support this reading method?
All Plextor CD-RW drives, UltraPlex 32max, and UltraPlex 40max/Wide
CD-ROM drives.
P-CAV (Partial Constant Angular Velocity) Reading
Method
P-CAV is similar to CAV, except that the maximum read speed (green)
is reached before the end of a full disc. The maximum read speed peaks
sooner than CAV towards the end of the read, as the spindle motor speed
decreases to maintain a constant data throughput. Effectively, P-CAV
is a combination of CLV and CAV.
Which drives support this reading method along with CAV?
PX-W12432Ti/e and PX-W8432Ti
CLV (Constant Linear Velocity) Writing Method
With CLV, the write speed (green) remains constant throughout the write.
In order to achieve this, the spindle motor's RPM (yellow) must spin
at maximum speed at the inner part of the disc, and then gradually slow
down as the laser moves toward the outer part of the disc. The circumference
of the disc increases as you move from inside to outside, causing larger
amounts of data to pass through the laser in the same amount of time.
The motor speed must decrease to compensate for this increased throughput
and provide for a steady write speed.
Which
drives support this writing method?
All Plextor CD-RW drives.
Z-CLV
(Zone Constant Linear Velocity) Writing Method
Zoned-CLV was introduced with the PlexWriter PX-W2410TA and PX-W2410TU
drives as a new technology for writing discs. Zoned-CLV combines several
different technologies; CLV, BURN-Proof and PoweRec-II.
There are three zones, each with its own write speed. For example, the
first zone is written at 16X until the write process reaches 6 minutes
into the disc. BURN-Proof then pauses the write process. PoweRec II
is then used to determine if the media supports the next higher speed
of 20X recording. This process repeats at 16 minutes into the disc to
determine if the media supports the final speed of 24X for the rest
of the write. The graph illustrates the write speeds of the three zones
for the PX-W2410TA / PX-W2410TU.
The
performance graph for PX-W4012TA will look similar to this graph, except
that there are now 4 zones and the final stage of write will be at 40X,
given that the media quality is sufficient.
Which
drives support this writing method?
PX-W2410TA, PX-W2410TU and PX-W4012TA
