On Mon, Jul 12, 2004 at 08:34:22PM -0400, David V. Corbin wrote:
> More seriously. I wonder how good the rotational stability is on the drive.
> Mny of the reasons for using "hard sectored" media was because a) Drives
> "wobbled", and b) Accurate timing electronics were "difficult".
I'd say it was because at the time, the predominant methods were either
hard-sectoring (which is easy to key off of), or, for multiple platter
drives, a servo *surface*. When you have only a single platter, filling
the bottom surface with servo data kills your capacity.
Also, keep in mind that the RK11-C, an early Unibus RK05 (RK03?) controller
was made of several dozen "FLIP-CHIP" modules. Any design decisions that
could keep that controller as small as possible would be a big win in terms
of manufacturing cost. The RK8E was several quad-height boards (approx one
square foot each).
The RL01 came out a few years later with embedded among the sectors. This
was a pretty good advance in drive technology. It's handy that the same
packs were used with both the RL11 and RL8A controllers. At the time I
first started getting into OMNIBUS PDP-8s (1984), I chose to go with an
RL01 ($150 shipped) and an RL8A (~$600) rather than an RK8E ($450?) and
adding another RK05 to the one I already had. Even in 1984, finding a
16-sector pack wasn't easy, but RL01Ks were available for nearly nothing
(businesses were switching to RL02s) 5MB per drive (RL01) vs 2.5MB (RK05)
was nice, too.
-ethan
--
Ethan Dicks, A-130-S Current South Pole Weather at 13-Jul-2004 01:30 Z
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Ethan.Dicks_at_amanda.spole.gov http://penguincentral.com/penguincentral.html
Received on Mon Jul 12 2004 - 20:44:04 BST