Found some info on IntelliPower on anandtech site:
http://www.anandtech.com/stora...howdoc.aspx?i=3161&p=2
The Western Digital drive's IntelliPower algorithm, which varies the rotational speed between 5400RPM and 7200RPM, dictates the Western Digital's rotational speed. Despite this variable rotational speed, Western Digital specifies the same average seek time as Seagate.
Edit: Well not sure about the above info I quoted from anandtech..
Different drive but check here:
http://www.storagereview.com/1000.sr?page=0%2C1
Cliff notes -- looks like IntelliPower spins close to 5400 rpm
The manufacturer is careful in not directly citing spindle speed, instead nominally positioning the Caviar GP as a "7200 RPM-class" drive. Under its "IntelliPower" moniker, WD claims a "A fine-tuned balance of spin speed, transfer rate and cache size designed to deliver both significant power savings and solid performance." Some folks have misinterpreted some admittedly vague specs on WD's website. Under "Rotational Speed," the manufacturer cites "IntelliPower (5400 to 7200 RPM)." This does not mean the drive dynamically changes its spindle speed during operation... indeed, such a feature would entail considerable mechanical engineering and would in many ways defeat the point -- rapidly accelerating and decelerating the spindle's speed would increase rather than decrease net power draw. Rather, the IntelliPower term indicates that the GP family as a whole does not have a set spindle speed (nor a set buffer size, for that matter). Different capacity points may feature differing spin speeds and buffer sizes. For those that must know, WD admits "sub-6000 RPM operation" for the 1-TB Caviar GP (more on this on the following page).
The next page:
We have to take a different approach when assessing the Caviar GP's seek time since WD does not explicitly give users the drive's spindle speed. The GP turns in a measured access time of 15.0 ms, a score that lags the 7200-RPM WD7500AAKS by a significant margin. The WD7500AAKS's measured seek time when accounting for 4.2 ms of 7200 RPM latency is 9.5 ms (missing the firm's claim by over half a millisecond). Assuming the GP also shares such a seek time, that leaves us with 15 ms [measured access time] minus 9.5 ms [assumed seek time] which equals 5.5 ms,
almost exactly the rotational latency associated with a 5400 RPM spindle speed.