Unix filenames and drum memory (was: Files as files)

From: Allison J Parent <allisonp_at_world.std.com>
Date: Fri Jun 12 14:14:25 1998

<> ObCC: I just noticed /dev/drum on a Dec here. Now I *know* there
<> is not a drum on this thing, so this must be a holdover from some
<> earlier implementation of some Unix. True? Were filesystems on
<> drums managed the same as those on disks? I don't see any reason

Drum is serial storage just like disks. What distinguished some drom
is that ther stored words using multiple parallel heads making them very
fast. On PDP-10 I used in 70/71 had a 128kw swapping drum used to hold
the swap file. It's my understanding (and memory) it rotated at 1200 or
1800 rpm and stored 18 bit parallel words.

I've also used a PDP-8 that had RS/RF08 disk that was structured like a
drum with 12bit parallel access (32kw per platter). It was also quite
fast.

In all aspects durms and disks are the same thing.

<> why they wouldn't be, offhand. But I thought drums died out before
<> Unix appeared. Does anyone still have a functional magnetic drum
<> memory? That would be one _awesome_ peripheral. :-)

It didn't!

<No, no functional drum, but I own _parts_ of a drum from
<an SIEMENS 2002 - this wasn't a storage drum like later
<on, this computer stored the (working) REGISTERS on the
<drum (Background: the 2002 was the first fully transistorized
<computer). Thats prior to core memory tek.

Core predates transistors. The TX1 and TX2 were the mostly transistor
machines that also had core. They had some tubes(valves) as the high
current pulse drivers for the core drivers. I think Mark1 or Whirlwind
(all tube) had core.

Another use for drums was bit serial machines where register and main
memory were serial in nature and stored on multiple tracks of the drum
(or disk).


Allison
Received on Fri Jun 12 1998 - 14:14:25 BST

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