> > > I'm also still not sure how many ``some'' amounts to.  Is it commonplace,
> > > or rare?  Something that only expensive drives do?  (Most drives still
> > > have RPM numbers associated with them; if they achieve the differing
> > > densities by rotating at different speeds, then a single RPM is at best
>  [...]
> > I'd say all modern drives have varying numbers of sectors per track... and
> 
> So if a modern drive lists a single RPM rating, what (if anything) is one
> to make of that?

I make of it that the inertia of the platter(s) is still (even in a
modern drive) too high to change RPM on the fly. More sectors per
cylinder in the outside tracks doesn't mean the drive runs at lower
RPM when it's accessing those tracks.

Think vinyl records, not CDs.

	-- Robert