[TUHS] /dev/drum

William Pechter pechter at gmail.com
Sat Apr 21 03:16:50 AEST 2018

Noel Chiappa wrote:
>     > From: Warner Losh
>     > Drum memory stopped being a new thing in the early 70's.
> Mid 60's. Fixed-head disks replaced them - same basic concept, same amount of
> bits, less physical volume. Those lasted until the late 70's - early PDP-11
> Unixes have drivers for the RF11 and RS0x fixed-head disks.
> The 'fire-hose' drum on the GE 645 Multics was the last one I've heard
> of. Amusing story about it here:
>   http://www.multicians.org/low-bottle-pressure.html
> Although reading it, it may not have been (physically) a drum.
>     > There never was a drum device, at least a commercial, non-lab
>     > experiment, for the VAXen. They all swapped to spinning disks by then.
> s/spinning/non-fixed-head/.
> 	Noe
Just a note... back in my old DEC days I went around and installed a
thing called the ML11-A (IIRC).
It was a Massbus box of MK11/MS750 memory arrays interfaced to a disk
emulation controller.

Plug it on your Massbus, format the memory with the disk formatter and
you have something like
an RS04 swap device made out of memory with no rotation delay.  Consider
it an early SSD.

It used plain old PDP/VAX memory (and could format and bad block out ECC
errors so the memory
didn't have to be perfect) and was software compatible (I think) with
the RS04...

I installed one at the AT&T/NY Bell site next door to the World Trade
Center back in 84-85 or so.

I wonder if it was still running on 9/11.  Word was Unix really was
improved on the 11/70 boxes without a huge investment on new gear. 
Quick swap was a big help on heavily loaded boxes.

Loved seeing the diag run tests and light the fault light on the box of
memory.  Also had a write protect like every good drive should.


Digital had it then.  Don't you wish you could buy it now!
pechter-at-gmail.com  http://xkcd.com/705/

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