Re: ZipGS card

[Eric Smith <eric@brouhaha.com>]

I wrote:
> The technical issue with the 400K drive is that they need a PWM motor
> speed signal which the Mac hardware generated.  Unidisks, 800K drives,
> Apple 3.5 drives, and Superdrives generate their motor speed control
> internally.

Wayne Stewart wrote:
> I've never tried it but I'm guessing that hooking the 400k mecanism to
> a daisy-chain card might work.

I don't think that will help.  The daisy-chain card doesn't generate
the PWM motor speed control signal, and none of the >400K drives provide
accessto their internal PWM motor speed control on their external connector,
and in any case, the motor speed depends on the track position, which
would most of the time not happen to be the same as that of another drive
on a daisy chain.

Apparently the 400K drive will work on a UDC card.  I don't have a UDC
so I can't confirm it myself.

When Apple introduced the Lisa 2 upgrade, which included a 400K 3.5"
drive, they had to add a small "Lisa Lite Adapter" card to generate the PWM,
because the original Twiggy drives in the Lisa had the PWM generation in
the drive.  The Lisa Lite Adapter was installed in the bottom of the
drive cage.  The Lisa 2/10 AKA Macintosh XL uses a different I/O board that
does have the PWM generator integrated, so it doesn't need the Lisa Lite
Adapter.

Eric