Re: CBM 8280
Date: 1999-08-31 07:05:26

CB>On Mon, 30 Aug 1999, Nicolas Welte wrote:

CB>> Geoff Oltmans wrote:
CB>> > I thought the "QD" format on 5.25" disks still used DD disks, only with
CB>> > double the number of tracks (80 vs. 40)?
CB>> Not exactly, real QD disks were tested and approved for that track
CB>> density. I think they are physically the same as DD disks, but were more
CB>> expensive.

CB>The question often occurs:  What is the difference between the various
CB>densities since the coating seems to be the same for SD, DD and QD.  Also
CB>what is the difference between single and double sided since there is a
CB>magnetic coating on both sides of single sided disks.

CB>The best answer I have seen was in the letters column of Electronics Now
CB>several years ago by a former employee of one of the manufacturers.
CB>He stated that the most expensive part of disk manufacturing is the
CB>testing and certification.  Single sided disks are not disks that
CB>failed on the second side, but disks that were never tested on the second
CB>side.  Double density disks are disks that were tested at double density, 

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At one time there were disks that were only coated on one side, they are
rare collector's items now.
Commodore in their Disk System User Reference Guide (182) says: Any
'soft-sector' single-density or double-density certified diskette will
work well with Commodore disk units. However, for the 8050 and 8250 disk
units, double-density diskettes are recommended.
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