working magnetic drum stores?

From: Tony Duell <>
Date: Thu Mar 25 22:47:27 2004

> On Thu, 25 Mar 2004, Jules Richardson wrote:
> > Just out of curiousity, does anyone still have a working drum storage
> > device? wondering if any working examples have survived...
> I've got a fixed head disk drive...kinda sorta like a drum except it's a

The big difference is that the disk has flying heads which essentially
set their own working clearance, the drum has haads fixed to the chassis
(which are adjustable for running height when the drum is set up). You
need a pretty low run-out in a drum's bearings.

Incidnetally, I have a graphics display for a PDP11 using a fixed head
disk. The disk rotates once per video frame (or maybe field, I forget).
The video data is recorded using analogue FM recording on a track of the
disk -- 3 tracks for R,G,B, and you can switch heads to switch between
images. There's some electronics to DMA data from the PDP11's memory (it
connects to a DR11-B interface), feed it into a DAC and FM modulator, and
record it on the disk.

> > seem good though so I might see if it can be coaxed into spinning) - but
> > a working demonstration would be great hooked up to one of the 1960's
> > machines.
> You can try making one by experimenting with paper rolls and cassette
> tapes and heads.

It's not hard to do this if you don't mind the head touching the media
(tape) as it does in a cassette recorder, but the life of the tape is
probably too short to use for serious data storage if you do this

Received on Thu Mar 25 2004 - 22:47:27 GMT

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