McKown, John wrote:
-----Original Message-----
From: IBM Mainframe Discussion List
[mailto:[EMAIL PROTECTED] On Behalf Of Paul Gilmartin
Sent: Thursday, July 12, 2007 1:57 PM
To: IBM-MAIN@BAMA.UA.EDU
Subject: Re: Track size and maximum single volume data set size
On Thu, 12 Jul 2007 14:34:17 -0400, J R wrote:
Well, I was always aware of the trade-offs, i.e. bit density
at the center v. bit density at the outside, but I wasn't
aware that anything was ever done about it with variable
data rates, etc.
CD players, like the original Macintosh 390 K floppy disks,
vary the angular velocity inversely with cylinder radius
in order to have both uniform linear density and uniform
data transfer rate.
-- gil
Right. Disk drives are generally CAV - Constant Angular Velocity - aka
the RPMs never change (not, not Redhat Package Manager files for you
Linux people <grin>). Optical drives (CD, DVD?) seem to be CLV -
Constant Linear Velocity.
No more. It is true for audio equipment, it WAS true for early CD-ROM drives.
CLV was the most limiting factor for "speeding up" CD drives.
Since 8x, or 10x drives CLV is no longer used. Current CD-ROM drives use ZCAV - Zone CAV. That's why you have 52x *max*. Real speed depends on zone.
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