Bad Classic Operating Systems (was: Micro$oft Biz'droid Lusers)

From: Ethan Dicks <>
Date: Tue Apr 23 12:53:57 2002

--- "Peter C. Wallace" <> wrote:
> On Mon, 22 Apr 2002, Richard Erlacher wrote:
> > I had a colleague who had a couple of "DF32" drives for his PDP8E...
> > which he was never able to utilize, and I've always wondered just how
> > those drives, with their small capacity, fit into the scheme of things.
> >
> > Dick
> >
> Isn't the DF32 a 32 Kword fixed head drive? I think it was used for
> multi-user PDP8 systems (like a drum)

That was a common use because they were word addressable (not block
addressable), write-protectable by 25% increments (four toggle switches)
and *fast* - no seek, just rotational latency.

OTOH, they _could_ be used as a scratch disk for a compiler, or anything
else. You _can_ put a filesystem on them, somewhat useful if you gang
four of them together (1 DF32 + 3 DS-32) - 128KW total.

I presume there is an OS/8 driver for them. I have never tried. The
machines that I have with DF-32s, do not have enough core for OS/8, and
in any case, I believe my platters are abraded away (the heads do not
retract as with newer drives, leading to wear on the plated surface).
The best I was ever able to manage was to write a program to flash the
state of the rotation sensor in the LINK bit to prove that I'd rebuilt
the sensor (it had caught fire before I got it).

Mechanical wear of the data surface was such a problem that the drives
were designed to have the motor and the electronics seperately power
down. For the most part, DEC had customers switch the drives on and
leave them spinning perpetually. It'd be like leaving on four table
saws (similar size motor).

Interesting drives, but impractical for general-purpose use.


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Received on Tue Apr 23 2002 - 12:53:57 BST

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