Re: Did the Apple II use single-density 5.25" drives?

[Michael J. Mahon <mjmahon@aol.com>]

Michael Black <et472@ncf.ca> wrote:
> On Thu, 6 Jun 2013, barrym95838 wrote:
> 
>> It's been many years since I fired up my old Franklin, but I seem to >
>> remember that it had a modified DOS 3.3 system master (called FDOS, I >
>> think) that, among other things, allowed the internal drives to read and
>> > write 35-track and 40-track disks seamlessly.  What I never discovered
>>> > is whether or not the standard Disk ][ drives were able to position >
>>>> their heads as far in as the internal Franklin drives.  I suppose that
>>>> I > could have tried booting the modified system master on my //e, but
>>>> I > never did, for some reason.  It might have been a good reason, but
>>>> I > just don't remember.
>> 
> That's interesting.  The Apple drives may have been able to do 40 tracks,
> perhaps it was easier to just use the same drives minus the controller
> board that were standard.  Who knows.
> 
> I mentioned that the Radio Shack controller for the Color Computer only
> did 35 tracks, and it also only did single side.  So there were various
> third party ROMs to make better use of the better drives.  I used
> something that turned out to be unlike the rest (or unlike what Radio
> Shack went to when they finally adapted to the newer drives).  I can't
> remember what was standard, see the floppy as one single unit so the
> files were spread over both sides, or treat it as two single sided
> drives.  I think the former was standard.  Anyway, the ROM I used was the non-standard.
> 
> So I have a few years of files using that odd setup.  And the ROM is
> actually an eprom lying around somewhere, I have no idea if it's still
> good.  And the ROM only works with the original CoCo, not the III.  SO I
> hvae to dig through layers if I want to get at them, and then no easy way
> to transfer them.  I think a few of those files would be nice to have.
> 
> But the point is, there were various schemes in those days by various
> companies to get more onto the floppies, and they were fine, until you
> wanted to use the floppies to transfer files, at which point the extra
> and thus incompatible space became a liability.

Right. The Shugart 390 drive was the first Apple drive, and the cam used
for head positioning was guaranteed good for 35 tracks, and could actually
do 36 tracks (yes, there were early DOS mods for that ;-).  

Later drives were made with positioned that could do 40 tracks, and the
media was capable of reliable use on those shorter inner tracks. But for
only a few percent improvement in capacity, you had to deal with 1) older,
incompatible drives, 2) older, less reliable media, and 3) the continued
need to use the lowest common denominator 35 track standard for disks that
are distributed. 

All things considered, not worth the trouble. (Maybe Apple learned from the
lengthy 13-sector to 16-sector transition, when there were many fewer Apple
II's.)

-michael - NadaNet 3.1 and AppleCrate II: http://home.comcast.net/~mjmahon