17 Jul
2018
17 Jul
'18
10:20 a.m.
On 07/17/2018 09:50 AM, Eric Smith via cctalk wrote:
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.
It was probably one of the more insane things that Apple did. 871K
using variable speed spindle motors (very irritating if you were a user)
and GCR. Just across the street on Bubb Road, we were getting 960K
using GCR on stock Micropolis drives in 1978. No fancy zoned recording
schemes or non-standard drives.
The Apple Mentality: NIH sometimes backfires badly.
--Chuck