[TUHS] /dev/drum

Clem Cole clemc at ccc.com
Mon Apr 23 03:37:27 AEST 2018

On Sun, Apr 22, 2018 at 1:01 PM, Lars Brinkhoff <lars at nocrew.org> wrote:

> Dan Cross wrote:
> > Why was it called drum? I imagine that's historical license coupled
> > with grad student imagination, but I'm curious if it has origin in
> > actual hardware used at UC Berkeley. Clem, that was roughly your era,
> > was it not?
> Seems like the Project Genie 940 at UCB had a drum.  Maybe someone
> wanted to carry the tradition forward.

​The 'someone' in all of this was Bill Joy (wnj).​  As I said, in those
days, all of us knew of older systems that used 'paging drums' - it was
pretty common term for the hunk-a-storage that the system dedicated to be
available to page itself.   it really is just like the fact that by the
time of the VAX, DEC was not shipping core memories at all (and few 11's
shipped with core either as the thanks to Moore's law, the price of
semiconductor memory had dropped), so calling the main system memory 'core'
was obsolete.   Thus, the UNIX term 'core dump' was really meaningless.
[In fact, Magic, the OS for the Tektronix Magnolia Machine has 'mos dump'
files - because I did that].

But the term 'core file' stuck, tools knew about, as did the programmers.
 The difference is that todays systems from Windows to UNIX flavors stopped
needed a dedicated swapping or paging space and instead was taught to just
use empty FS blocks.  So today's hacker has grown up without really knowing
what /dev/swap or /dev/drum was all about -- in fact that was exactly the
question that started this thread.

On the other hand, we still 'dump core' and use the core files for
debugging.  So, while the term 'drum' lost its meaning, 'core file' - might
be considered 'quaint' by todays hacker, it still has meaning.


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