[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Disk II Half - Quarter Tracks



Tristan Mumford wrote:
Michael J. Mahon wrote:


RedskullDC wrote:

-snip-

I did once experiment with the track widths to see what could be
achieved.

Using a stock standard Disk][, writing on every half track proved to be
unreliable.

-snip-

The DOS3.3 track stepping routines would need to be modified to support
3/4 track spacing, but it would be possible to easily gain an extra 50%
storage capacity
on a disk][ this way.

Actually, just 33% more data--and likely *much* less reliability.


Differing results may be obtained using different disk][ drives, as I
have no idea of
the manufacturing tolerances of the read/write head widths.

Right.


Agreed. There _is_ another option that has crept into my deepest, darkest
thoughts though.
Using a different type of drive. Looking at the disk ][ etc. signals it
doesn't seem completely out of the realm of possibility to connect a PC
drive to a disk ][ style controller. For instance, every stepper I have
seen on a PC drive has the 4 phases(?) exposed without dismantling, at
least much anyway.
Blah blah... proprietary drive that nothing else could read ... blah. Anyway
my point is that utilising something designed for higher density would
allow it. The main question would be head voltage. Higher densities usually
use lower voltages.

But the head is controlled by in-drive electronics, so that shouldn't be
a problem for the controller.  And virtually *all* floppy drives predate
3.3v logic.

The bigger problem is the bit rate.  The Disk ][ controller is designed
around a 250kHz bit rate, and higher density drive all used much higher
bit rates.

More tracks would still improve capacity, but you'd be stuck with low
bit rates.  Of course, since we're talking custom modifications here, it
might be possible to lower the rotational rate along with the bit rate
to get more bits per track...

-michael

NadaNet networking for Apple II computers!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it's seriously underused."