Another disk imaging project

Scott Stevens chenmel at
Wed Aug 3 21:55:43 CDT 2005

On Wed, 3 Aug 2005 10:27:01 -0500
Patrick Finnegan <pat at> wrote:

> I know a lot of people that wouldn't build ANY hardware.  Even more 
> people (like myself) would rather spend the money for a catweasel than
> try to find parts and build something that doesn't have the 
> functionality of a catweasel.... Do you think you'll get your WD chip 
> solution to read Apple ][ or C64 (1571-written) disks?  I'm doubtful
> at best.  That's a huge volume of the disks I've got laying around and
> eventually want to make images of.

I think the beauty of an open design is that you in particular don't
have to be capable or motivated to build the hardware yourself, but
there are multiple other people who are capable and (possibly) willing
to build one for you.  A 'closed' design lives and dies at the whim of
the person who designed (and built) it.  

A publised 'open' design constructed with TTL gates could, for example,
be constructed by someone who prefers CMOS or ECL (!) who is motivated
to adapt the design.  (I know, as a packrat with a huge junkbox, that
when I see a logic circuit I want to build I always immediately begin
adapting it to the TTL I happen to have on hand.)


(stepping into a discussion where I am a latecomer, and don't mean to
step on feet or exceed my expertise)- Isn't a disk controller really
just a specialized logic state machine?  When I studied the 1771 in tech
school I remember it as being fairly rudimentary stuff, i.e. nothing
that a general purpose Micro couldn't be coerced into doing.  In fact,
the whole reason for the dedicated controllers of the past was that when
the whole system's 'brain' was just a Z80 or 6800 (or even just a 6502)
processor, a hardwired 'dedicated peripheral controller' design was the
only way to 'extend the machine' to do as complex a task as control a
floppy drive.  These days, we're not so resource-starved that the
machine it's 'plugged into' only has a simple 8-bitter as it's sole CPU
(i.e. the Z80 chip isn't a $75 item that the whole rest of the machine
surrounds,) so it seems like if all the resources of a Z80, or a PIC, or
similar processor were thrown at the task, with some additional generic
(i.e TTL gates) hardware outboard, it could be a highly flexible
controller.  (pardon my processor bias in the above.  plug in your
favorite arch. as desired) 

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