12 Jan
2011
12 Jan
'11
3:25 p.m.
On 12 Jan 2011 at 21:24, Tony Duell wrote:
Now, if you had a positioner that could only move half
the distance
from outside rim of the platter to the spindle, but you had 2 heads
per surface suitbleyoffset (so that you could access 2 tracks on each
surface without moving the psoitoned) then I would claim that both of
thos tracks were part of the same sylinder. For example, if you had 4
data surfaces (and thus 8 hards in this drive), I would say that a
'cylinder' contains 8 tracks, even though the arrangement of said
tracks doesn't look like a physical cylinder any more.
Well, drives like that certainly existed, as well as drives that used
a single positioner located between two or more spindles that moved
heads on all drives (think "push pull" or even an X-shaped positioner
arm.
The CDC 808 recorded 6 tracks in parallel (I still have a head from
one) on each head, with IIRC, servicing two spindles on on upper
positioner and two spindles on a lower positioner. Transfer was 12
bits in parallel.
I know that the 821 (a very rare drive; AFAIK they were specified in
some Special Systems RFPs and turned to trash as soon as the 844
drives became available) was similarly configured pretty much the
same in appearance. I don't know if any other parallel drives were
made by CDC--at least I never used any.
--Chuck