On Thu, 4 Jan 2001, Richard Rauch wrote:
> So if a modern drive lists a single RPM rating, what (if anything) is one
> to make of that?  Average-per-cylinder?  Average-per-sector?  Minimum?  
> Maximum?  Or is it some kind of effective RPM (based on some nominal
> geometry and the speed at which a single block passes under the drive
> head)?

I don't know of any hard drives that change their rotation speed... the
RPM is just that--the number of revolutions per minute. On the inside of a
platter, that may be 100 sectors, and on the outside, it may be 200
sectors, which gives you twice the data rate on the outside.

On the other hand, CDs are constant linear velocity (at least
originally)... the disc spins slower when the head is at the outside than
it does when the head is at the inside, so you get a constant data rate of
150Kbytes/second or so. (You can see this if you have a portable CD player
with a clear window so you can see the CD spinning... it's noticeably
slower at the end of the CD). Some CDROM drives are constant angular
velocity though, and will read faster on the outside than on the inside...
I believe many Plextor drives are like that.