Re: Info on 3.5 floppy drives sought

[dempson@actrix.gen.nz (David Empson)]

In article <2ua8okEbbs@uni-erlangen.de>,
Toerless Eckert <eckert@delos.informatik.uni-erlangen.de> wrote:
>
> I have an apple2gs but never used it as a 2gs (okay, another story).
> I don't have 3.5 drive so now i'm looking for one. First i wanted to
> understand what different options i have, so here is just the questions
> that garble in my mind. Hopefully somebody can fill me up with insight
> into this matter:
> 
> - What different 3.5 drives will work on the apple2gs internal IWM
> controller ? (there's something like unidisk i've heard or the like) ..

The best option by far is an Apple 3.5 Drive, an Apple SuperDrive, or a
third-party clone of either of these drives (Applied Engineering and
AMR made versions of each of these drives).

If you use a SuperDrive or a clone of one, it will only be able to
access 400k and 800k disks.  You need a special controller card to
support 720k and 1.44MB (high density) disks.


You can also use a UniDisk 3.5, which is the type of drive supported by
the Apple IIc (and can also be used on a IIe with a controller card,
and on a IIc+).

The UniDisk 3.5 is considerably slower than the Apple 3.5 Drive when
used on a IIgs, and using one will limit the software you can use (many
games, copy protected programs and "demos" expect an Apple 3.5 Drive
or equivalent).


You _might_ be able to use the Macintosh Plus external drive, but you
won't have an eject button, which is a major problem.  You cannot use
the earlier Macintosh 400k drives because they need a timing signal
which is not provided by the IIgs.  The Mac Plus drive might have the
same problem.

> - What's the capacity ?

400k (single side disk) or 800k (double sided disk).

> - How does it read the data. Only thing i know is that old macintosh
>   drives used to read with GCR and that they had different rotational
>   speeds depending on the track. Do the 3.5 drives for the apple2gs 
>   exploit the same mean of access ?

The low level format is identical to that used by the Macintosh - GCR
with variable rotation speed in 16-track bands; 512 byte sectors and
80 tracks.

The only differences are the file system (the Mac uses MFS or HFS, the
IIgs usually uses ProDOS) and the IIgs doesn't make use of the "tag"
bytes at the start of each sector.

> - Are any of the drives sold for macintosh compatible with the
>   internal controller on the apple2gs ? How about the correct adapter
>   cable pinout ?

The drive connector pinout is compatible between the machines.  You
may have minor problems using third-party drives, such as having to
keep a disk in the drive or the computer locks up when it polls the
drive (AMR drives have this problem).  I don't know if all third-party
drives are able to be daisy chained, and if they are, they might not
work with a daisy-chained UniDisk 3.5 or 5.25" drive.

> - what will i gain through a plug in disc controller card, i.e.: what
>   kind of additional drives can i connect to one ? 

If you get the Apple SuperDrive card (originally called the Apple II
3.5 Disk Controller Card, and it has recently been removed from the
Apple price lists) then you can use a SuperDrive in its "native" mode
- it can read and write 720k and 1.44MB MFM formatted disks, as well
as 400k and 800k GCR disks.

> - How much for a apple2gs 3.5 drive by now ?

Around $50 is the sort of price I hear for used Apple 3.5 Drives.
 
> Alternatively please answer the following question
> - Where's the FAQ that answers the above questions ?

I haven't looked at the FAQ for this newsgroup for a long time, but
this is certainly the sort of question it should be answering.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand