Re: How many floppies can I use with a Apple IIe

[Warren Ernst <wernst@gmail.com>]

On Oct 8, 4:19 pm, Rusty <rdek...@gmail.com> wrote:
> On Oct 8, 6:54 pm, Linards Ticmanis <ticma...@gmx.de> wrote:
> Other than needing a different controller, what are the differences
> between the "smart" 800k drive and the "dumb" 800k drive. Is it that
> the "smart" drive had more of the control electronics onboard so as to
> need a less-sophisticated controller, or was it something else
> entirely?
>
> Rusty D

The drive *mechanism* is identical. I've swapped drive mechanisms
between Unidisk 3.5's and Apple 3.5's without problems. So that's not
it.

The difference is in the electronics. The UniDisk has its own 6502
processor and (I think) 2 kb of RAM to act as a buffer for the
relatively slow and dumb //c (with newer ROMS) and //e (with Liron
card) . The Apple 3.5 Drive has no smarts or buffer, and it is
expected the host computer (A GS or early Macintosh) has enough speed
and smarts to handle the data stream. The SuperDrive uses its own RAM
and "smarts" to handle an Apple 3.5 Drive in a //e.

Otherwise, the UniDisk is slightly slower. It has a 4:1 sector
interleave while the Apple 3.5 has a 2:1 sector interleave. Each can
read and write disks formatted in the other, but the speed degrades
slightly when this happens. I seem to recall there being a utility
that would force a 4:1 interleave on the disks formatted with the
Apple 3.5 drive, (Copy //+ v 9.1 perhaps?), but I've never had the
need.

(Incidentally, from the "You didn't ask but I'm telling you
department", you can exchange the 800KB mechanism from an Apple 3.5"
drive in put in a 1.44MB High Density drive mechanism and make your
own SuperDrives. I made both of mine this way for about $5 each about
two years ago. They act as regular 800KB drives without the SuperDrive
controller, but since I have one they are plugged into it.)

-Warr