Re: Hardware musings

[Linards Ticmanis <ticmanis@gmx.de>]

Ben Rudiak-Gould wrote:

> * The only hope for cycle-accurate reading without extra hardware seems
> to be Stephen Thomas's code. It can be modified to flag only 10-bit sync
> for a few disk revolutions, and then all sync for another few; track
> length analysis could be done ignoring the high (sync flag) bit, and
> then the high bits from successive revolutions could be compared to
> distinguish 9 from 10-bit sync.

You're raising an important point here, the sync detection is not 100%
reliable due to rotational speed variations, thus if you want to get it
"right" every track has to be read a couple of times (at least three
times, so that you can get a "majority vote", but five or seven times
would probably be more reliable).

> * Syncing to track 0 sector 0 is easy if it exists, but what if it
> doesn't? There are non-bootable copy-protected disks. I see no reason to
> expect any hard bits on track 0 at all.

One would have to have the user select some other unique byte sequence
then, I guess.

> * Should track length and soft-bit analysis be done by the 6502, or on a
> modern machine? It depends on how much harder it is to transfer larger
> amounts of raw data between computers, which depends on each individual
> user's setup. Do we have to implement the analysis twice?

I'd suggest running it on the PC end.

> * The imaging process will be very slow, and a single disk image will be
> too large to fit on an 800K disk, even if track length analysis is done
> on the 6502. How many people are going to jump through the necessary
> hoops to image their disks? It seems very inconvenient.

Can't one at least assume a working ADT setup, i.e. a serial connection
between the Apple and another machine? Or is this going to exclude too
many potential users?

-- 
Linards Ticmanis