🚀 go-pugleaf

In article <1256@hoptoad.uucp> gnu@hoptoad.uucp (John Gilmore) writes:
>I don't understand why nobody has built magnetic disks that spin at
>a constant speed, but vary the clocking of data to the disk so that
>all the bits end up the same width on the media.  This means that you
>might get 30,000 bytes per track on the inside and 90,000 on the 
>outside -- but who cares?  On a SCSI interface, the system doesn't know
>where the tracks and cylinders are anyway.

See "Constant-density recording comes alive with new chips", Mark
Young, _Electronic Design_, Nov 27, 1986.

It shows how to solve the variable clock problem. It also talks about
how it is important the disk you are using not have its own clock
separator, which leaves out ESDI and SMD, with only ST506 as a
acceptable commonly available drive type. Also, the drive must have a
read amplifier with enough bandwidth to support the higher bit rate.

Of course, if you wanted to invent your own disk this would not be a
problem. And the improvement gotten from constant-density recording is
on top of any RLL improvements (multiplies). Then there's the question
of software. The OS now has to deal with differing number of sectors
per cylinder, what would this do to the Berkeley Fast File System?
Anyway, it's a good article and you should read it.
-- 
 The VT220 keyboard is an <iS<o standard. That means the French can
 hate it as well as the Americans.

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