New subject: floppy controller (summary?)

29 Sep 1999

In a message dated 09/29/1999 3:04:36 PM Eastern Daylight Time, 
ard(a)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.

...
   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

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