Re: Question: Hardware differences between Unidisk 3.5 and 3.5Drive?

[Wayne Stewart <waynes@intergate.bc.ca>]

Mark Cummings wrote:

> Just to add a bit to Wayne's extensive knowledge, the "Laser UDC" card can
> only run the Apple 3.5 drive (and 5.25), it is _not_ compatable with the
> Unidisk 3.5.
> The Unidisk 3.5 can also be used on a GS with the UniDisk3.5 driver
> installed.

 I have 2 UDC cards, the Laser UDC  card which wouldn't use the 3.5"
UniDisk while the vtech UDC card would.  While the card designs are
very different but because the ROMs are interchangeable I'd suspect the
same manufacturer. I'd suspect that 3.5" UniDisk support was dropped
somewhere along the line because if you were going to get the 3.5"
UniDisk drive, you could get the Apple controller card for only a bit
more when packaged with the drive.  If you bought the UDC card you
wouldn't likely choose the 3.5" UniDisk to use with it since Apple charged
twice as much for their drives.

Generally I prefer to use a platinum 3.5" with the UDC card since in an
accelerated Apple II it's faster as it can correctly utilize  a 2:1 interleave.

Actually the aftermarket drives would do the same but I think the
Apple drives look a bit snazzier than say the laser drive did especially
alongside a II+.
One annoyance with Copy II Plus and a number of other programs is
they all want to format 4:1 on an 8 bit computer. Only a few programs
offered a choice of interleave. One nice thing about the UDC card as
opposed to Apple 3.5" controllers is it lets you use the Copy II Plus bit
copy utility.

One problem with many UDC cards is with the eject button on the Platinum
3.5" drive. Mostly the second drives eject button didn't function and in some
cases neither button worked. I ended up wiring the eject button directly to the

eject mechanism in the 2 drives I use with a UDC card. A possible problem
with that mod is that the drive will now eject while in use. Maybe I'll try
that
sometimes just to find out just what happens.


    Wayne