spacewar at gmail.com
Tue Jul 17 11:50:01 CDT 2018
On Mon, Jul 16, 2018 at 4:58 PM, Fred Cisin <cisin at xenosoft.com> wrote:
> On the Lisa "Twiggy" diskettes, they made special provision to get more
>>> thumb prints.
> On Mon, 16 Jul 2018, Eric Smith wrote:
>> I imagine you're aware of the actual reason for the two diametrically
>> opposing jacket cutouts for the read/write heads.
> I'm NOT sure. I speculate:
> 2) To have two sets of heads. Either performance, or simply two single
> sided heads, to have felt pad instead of head to head pressure
The latter, two single single-sided heads, each opposed by a pressure pad.
Aside from the provision for extra fingerprints, a problem with this scheme
was that they varied the rotation rate depending on the position of the
head in use. Unfortunately since there was only a single actuator, when the
top head was near the inside, the bottom was near the outside, and vice
versa. Except for the middle few tracks, it was never fast to switch from
one head to the other without seeking. The logical disk organization was
all of side zero followed by all of side one, rather than by cylinder.
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