4 floppy disk drives on a PC?

[Patrick Finnegan]

Doc Shipley declared on Monday 17 January 2005 11:04 pm:
> Dwight K. Elvey wrote:
> > 1. A truely blank disk ( bulk erased ) can be formatted
> >  and written on by a 1.2M drive and will work in most
> >  cases on a 360K drive. This may written on by a 360K
> >  drive as well and still work on a 360K.
> > 2. Once a disk has been written on first by a 360K drive
> >  and then a 1.2M, it can only be read on a 1.2M drive!
> >
> > That's life.
>
>    No, that's wrong.  At least, it's not necessarily true.
>
>    I have formatted disks for an RX50 on the 1.2MB drive, written data
> to them on that drive, and used them on a PDP-11.  I have also used
> floppies to back up an RSX-11S disk on "real" RX50 disks, transcribed
> that to PC, overwritten them on the PC without a low-level format, and
> read them on the PDP-11.  I have had some floppies fail, but they
> always failed either on the RX50 drive *before* they were ever in the
> 1.2MB drive, or they failed format on the 1.2MB drive before they ever
> made it to the PDP-11.
>
>    I don't doubt the information I'm reading, that the track written
> by the 1.2MB drive is narrower than the track written by a native 360K
> drive.  I'll even stipulate that my experience is limited to writing
> disks for PDP-11s and the Altos 580 (DSQD I think; I haven't played
> with that box in a long while), so I can't speak to the reliability on
> other platforms.

Umm, the RX50s and Altos 580 floppies you've used are 80-track (96tpi) 
disks just like 1.2MB floppies.  360k floppies are 40-track (48tpi) 
disks.  So, they're the same track width as a 1.2MB disk, not a 360k 
disk.

Pat
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