> On Oct 1, 2024, at 11:30 AM, Chuck Guzis via cctalk <cctalk@classiccmp.org>
> wrote:
>
> On 10/1/24 07:54, Jon Elson via cctalk wrote:
>
>> The IBM 2314 was REALLY low tech. There was almost no electronics in
>> the drives! They has a read amp, a write amp and a hydraulic "stepper
>> motor" with mechanical detents that moved the heads in response to step
>> in and step out pulses from the control unit.
>>
>> IBM did know how to distill things down to the absolute minimum.
>> Remember, this was developed in the early 1960s and first shipped with
>> the first 360's in 1965.
>
> Hydraulic positioning was used in several early drives. The Bryant
> 4000/CDC 6603, for example, had containers to catch leaks. ISTR that
> the head assemblies weighed about 8 lbs each.
For that matter, the first hard drive (IBM RAMAC) used hydraulic positioners,
for both cylinder and track select I believe. It had only one or two heads, so
track switching was a mechanical operation and actually a lot more expensive
than changing cylinders.
> The Univac FASTRAND drum, on the other hand, used electromagnetic
> positioning, employing a mechanical lever adder to come up with a binary
> position.
>
> -C
Interesting. It reminds me of technology used on PLATO terminals, both in the
microfiche projector option and in the audio disc player: a set of pneumatic
pistons with stroke length scaled 1:2:4:8 so you could get any of 16 positions
by sending a 4 bit address to a set of 4 valves. It's the only place I've ever
seen where computer terminals had connections to pneumatic supply lines.
paul
