Reiability of wrong media (was: is out of 5-1/4" diskettes

From: Don Maslin <donm_at_cts.com>
Date: Fri Jan 22 00:29:09 1999

On Fri, 22 Jan 1999, Tony Duell wrote:

> [80 track 5.25" disks]
> > And they're pretty common on non-MSDOS systems. I far more 80-track DS
> > drives than 40-track of any flavour.

What the CP/Mers used to refer to as Quad Density.
 
> I've got a number of old IBM PCs and XTs so there are some 40 track
> drives around here, but also looking about I see a lot of 80 track drives
> - TRS-80 model 4, Sirius, Gemini, BBC micros, Torch XXX, etc, etc. The
> Whitechapel MG1 currently has a 3.5" drive in it, but I have the original
> 5.25" 80 track drive as well.
>
> Ouch!. I need to find a source of these disks...
>
> > > Interesting! I have never had a problem using even generic 48tpi disks
> > > at 96tpi.
> > > - don
> >
> > Nor have I, usually. I tend to treat all double-density 5.25" disks the
>
> So what an I doing wrong?

Don't know, Tony. All I can suggest is to degauss them first, but you
probably do that anyway.
                                                 - don
 
> > same. Some of the old ones I have were converted to be "flippy" 40-track,
> > and some time ago I found one such without a label. Not knowing whether it
> > really had been formatted flipped, I tried it out, using the
> > by-now-standard 80-track DS drive and a two-step circuit, and found it had.
> > "OK, so that's a flippy", I said to myself. A little later, I re-read the
> > catalogue -- and got a different listing! I had inadvertantly catalogued
> > side two, with the disk right-side-up -- and realised that the tracks must
> > not line up, so side two had two sets of data, going in opposite rotations,
> > with the tracks interleaved!
> >
> > So I have a three-sided 40 track disk :-)
>
> Kersqueeble (or something).
>
> I seem to remember that the track 0 (say) on the 2 sides of the disk
> doesn't line up on a true double sided disk. I also seem to recall that
> it's not offset by a whole number of tracks. I wonder if that's what
> happened to you - you interleaved the tracks written by the 2 heads on
> the 2 sides of the disk.
>
> No I am not going to try it.
>
> Talking of flippies, the 3" drives were stupid. All disks were double
> sided. Single head disks used them as flippies - some drives even detected
> the position of a notch in the disk and changed the colour of the drive
> active LED so you could tell which way up the disk was . Double-head
> drives had a little bracket that fitted into that notch and prevented you
> putting the disk in upside-down.
>
> So if you had flippy you could read side A in a double-head drive. But
> you couldn't read side B - it was spinning the wrong way to read it with
> the disk the normal way up and you couldn't turn it over to read it as a
> flippy. Well, you couldn't until you dismantled the drive and applied
> pliers and cutters to the bracket :-)
>
> -tony
>
>
Received on Fri Jan 22 1999 - 00:29:09 GMT