15 Nov
2007
15 Nov
'07
7:40 a.m.
On Wednesday 14 November 2007 15:18, Lee Inness-Brown wrote:
I was reading your thread about DDC head-per-track
drives.
I had a friend around 1980 that had one of these drives which he had
obtained as surplus from the US Air Force.
It used helium atmosphere around the disks to reduce friction. The disk
was 12" in diameter and spun at 33,000 RPM (not a typo), and so it would
produce considerable heat from friction if ordinary air were used, at least
that's what I heard at the time. It was intended as a substitute for
magnetic core (RAM) for mainframes. The disk latency was around 30
microseconds. Because the driving electronics were a lot slower then, the
rated random access speed was (as I recall) 50 microseconds.
One thing I've been curious about with regard to drives like that -- how many
heads/tracks does it have? How many _can_ such a thing have?
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin