Re: Apple II 3.5" Controller and SuperDrive problems...

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

<mkelsey@spam.eecs.wsu.edu> wrote:

> In article <1d5kp6z.kjh8ytffyqpuN@dempson.actrix.gen.nz>,
>       dempson@actrix.gen.nz (David Empson) writes:
> > <pubpc1@library.ucla.edu> wrote:
> > 
> >> Wrong, the UDC works with the Mac HD20.  I've seen one attached
> >> to an Apple IIe.  There are two models of UDC cards.  One is the
> >> older full size controller.  The second one is the newer, half
> >> size card.  The IIe that was connected to the HD20 used the full
> >> sized version.  I would think that the half sized card would
> >> retain the capability.
> 
> So what exactly is the Mac HD20?  Is this just an external SuperDrive?

No.  The HD20 is an old 20 megabyte hard drive that Apple made for use
with the Mac 128, 512 and Plus.  It connects to the floppy port on the
Mac, which means it is very slow (serial transfer instead of parallel).

With the introduction of the Mac Plus with its SCSI port, the HD20 was
replaced with the HD20SC (SCSI version).  There is no problem using them
on an Apple II, but the original HD20 doesn't work except with a UDC
card.

> I have connected a SuperDrive to my CPS UDC (half-sized I'm guessing)
> but it only recognized the drive as an 800K which I believe to be
> a limitation of the firmware, but perhaps in the hardware, as well.

Definitely the firmware, and almost certainly the hardware as well (it
can't handle MFM-encoded data, I expect, not to mention double the data
rate for high density disks).

> > Can anyone else out there confirm that they have failed to get a UniDisk
> > 3.5 working on a UDC?  If so, can you please let us know which UDC
> > version it was, and any other identifying characteristics.
> 
> If I had a UniDisk 3.5, I'd test this out.  Unfortunately, I don't think
> a Macintosh external is the same thing.  In fact, I distinctly recall
> the the UniDisk 3.5 having a 6502 built into the drive case.

Correct.  The UniDisk 3.5 is effectively an Apple 3.5 Drive with a
replacement controller board inside the drive that has its own 65C02,
RAM, ROM and IWM (disk controller).  It uses an intelligent packet
protcol to communicate with the computer, and the transfer rate is about
half that of an Apple 3.5 Drive.

The Macintosh 800K external drive (without eject button) is the same
drive mechanism, but with no interface circuitry (the computer controls
the drive directly); there is a small amount of rearrangement going on
in the Apple 3.5 Drive which is required for Apple II support (and this
drive also supports the eject button).

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand