4 floppy disk drives on a PC?

[Doc Shipley]

Dwight K. Elvey wrote:
> Hi Eric
>  I think he means that as long as he stays on that drive,
> he has no issues. The write problem is obvious to anyone
> that thinks about it a little ( I hope ).

   I don't just stay on that drive.  If I did, I wouldn't need it in the 
first place.

> 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.

   I *can* say that in writing, overwriting, transcribing, and reading 
RX50[0] floppies between a real PDP-11 and a Linux PC with a 1.2MB 5.25" 
drive, track width has never been an issue.  The few disk failures I've 
had never got far enough to bring that into play.


	Doc

[0] Both original NIB RX50-formatted 3M floppies, and 1.2MB DSHD 
floppies formatted according to Pat Finnegan's fdformat/superformat 
parameters.