floppy controller IC (was Re: Fixing a PET?)

From: Don Maslin <donm_at_cts.com>
Date: Thu Sep 30 00:04:30 1999

On Thu, 30 Sep 1999 Glenatacme_at_aol.com wrote:

> In a message dated 09/29/1999 3:04:36 PM Eastern Daylight Time,
> ard_at_p850ug1.demon.co.uk writes:
>
> > > Interestingly, with this system when a disk is formatted it is required
> > that
> > > the number of TPI be input. This is then stored on the disk so I might
> > have
> >
> > I assume that's total number of tracks, or something similar.
>
> Yes, the total number of tracks.
>
> > LDOS (and related OSes) on the TRS-80s does much the same thing. When you
> > format a disk it asks you for the number of sides and number of tracks.
> > And provided the hardware is capable of handling what you ask for, it
> > will format and (correctly) use the disk.
>
> Interesting -- I'd _not_ be shocked to find out that the maker of the system
> I use "borrowed" the idea from RadShack.
>
> BTW my understanding is that all 5.25 diskettes made today are bin-sorted --
> that is, they shoot for DSHD and the fallouts are sold as DSDD. I have a
> number of "DSDD" diskettes here which work well when formatted with 50+
> tracks, although how this is possible with "40 track" DSDD drives I haven't a
> clue. Perhaps you do.

I think that you are confusing DSHD and 96tpi which are not necessarily
the same thing. Most DSDD disks will format to 96tpi (720k on 5.25"),
even the generics. But I have yet to successfully format a DSDD (360k)
to 1.2mb or a DSHD (1.2mb) to 360k.

                                                 - don
   
> > On the model 1, the original drives were 35track, but all later ones
> > could do 40 tracks (or a little more, like 42 tracks). Needless to say,
> > the extra storage, particularly on 'system disks' came in handy back then
> :-)
>
> Fortunately this system doesn't require "system disks" (the os is on an
> eprom) but I know what you mean. In a floppy based system a few extra KB can
> _really_ make a difference ;>)
>
> Regards,
>
> Glen Goodwin
> 0/0
>
Received on Thu Sep 30 1999 - 00:04:30 BST