18 Apr
2000
18 Apr
'00
5:37 a.m.
Hi,
I think I heard somewhere that magnetic drums are somewhat like core memory,
i.e. they retain their contents when shut off... I believe I read this in
the IBM 704 manual, so I'm not entirely certain that facts about those drums
(8192 36-bit words!) can really be applied to the drums I'm going to be
getting, which are from Vermont Research and are approximately 256K or so..
Also, does anyone know what other computer companies used drums from Vermont
Research? They're for my Interdata 7/32, but I know at least Varian used
Vermont Research drums... any others?
Will J
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18 Apr
18 Apr
6:09 a.m.
Hi,
I think I heard somewhere that magnetic drums are somewhat like core memory,
i.e. they retain their contents when shut off... I believe I read this in
Actually they are cylindrical disks with multiple heads in parallel so
that you can write a word or read one rather than serializing the bits.
Drums were used on PDP-8s, PDP-10s and likely others for small storage or
more commonly swapping out contents of memory. Think of this if you can
read or write a word in 1/1800(or 2400rpm) or a block of core eaqually as
fast swapping is viable to expensive and hard to get memory.
getting, which are from Vermont Research and are
approximately 256K or so..
Also, does anyone know what other computer companies used drums from Vermont
Research? They're for my Interdata 7/32, but I know at least Varian used
Vermont Research drums... any others?
Oh, I'd love to get one. the last time I played with drum was 23+ years
ago and it was a small 14bit wide by 8192 word affair I used as a fast
disk till it died mechanically.
Allison
3:31 p.m.
At 11:09 AM 4/18/00 -0400, allisonp(a)world.std.com wrote:
I think it is helpful to distinguish between two different devices.
One is a head-per-track disk, sometimes called a Fixed Head disk.
DEC had several of those devices on their machines. The one I am most familiar
with is the RC64 on my PDP-11, but there were also RF series drives for older
machines. The generally had a disk platter, like a normal disk, but unlike
a normal
disk they had one head dedicated for each track on the disk -- no seeks!
A drum, on the other hand, was cylindrical (hence the name). (The first audio
records were cylindrical too, incidentally). Some drums were
also head-per-track devices, but not all. Some had a head that moved from
place to
place along the drum. Univac called each such location a "position".
There is no inherent reason why a drum would not necessarily serialize the
data --
one could construct them either way, depending on the requirements.
I am familiar with a couple of cases where the data was most definitely
serialized: the
IBM 650 and the Monrobot desk-sized computer.
Jay
---
Jay R. Jaeger The Computer Collection
cube1(a)home.com visit http://members.home.net/thecomputercollection
Hi,
I think I heard somewhere that magnetic drums are somewhat like core
memory,
i.e. they retain their contents when shut off...
I believe I read this in
Actually they are cylindrical disks with multiple heads in parallel so
that you can write a word or read one rather than serializing the bits.
Drums were used on PDP-8s, PDP-10s and likely others for small storage or
more commonly swapping out contents of memory. Think of this if you can
read or write a word in 1/1800(or 2400rpm) or a block of core eaqually as
fast swapping is viable to expensive and hard to get memory. 
6:11 a.m.
I think I heard somewhere that magnetic drums are
somewhat
like core memory, i.e. they retain their contents when shut
off...
Drums are probably more analagous to the modern HDD
given that it is record by moving head on magnetic
media. That or a single grotesquely magnified loop
of magnetic tape.
--all based on academic study
Of course both the MT and HDD are persistent.
Perhaps there are even ex-drum repairmen on the list?
7:53 a.m.
I think I heard somewhere that magnetic drums are
somewhat like core memory,
i.e. they retain their contents when shut off...
Well, Drums are just a spcial kind of disk - it's a
geometrical phenomena - a disk where all tracks have
the same length :=)
Gruss
H.
--
VCF Europa am 29./30. April 2000 in Muenchen
http://www.vintage.org/vcfe
http://www.homecomputer.de/vcfe
6:33 a.m.
On Tue, 18 Apr 2000, Hans Franke wrote:
Which is why we still refer to disk data structures as
'cylinders'... on the surface of a drum, that's the geometric shape
they occupy.
On my old Bendix G-15, the clock tracks were also on the drum,
allowing the use of a standard 1/4hp induction motor. I have also
seen reference to slow-cycling a drum computer by disconnecting the
motor and turning the shaft by hand.
And now they have 340M hard drives built into FlashCard memory
chips for my digital camera......
Cheerz
John
I think I heard somewhere that magnetic drums are
somewhat like core memory,
i.e. they retain their contents when shut off...
Well, Drums are just a spcial kind of disk - it's a
geometrical phenomena - a disk where all tracks have
the same length :=) 
7:37 a.m.
On Tue, Apr 18, 2000 at 08:33:15AM -0700, John Lawson wrote:
Which is why we still refer to disk data structures
as
'cylinders'... on the surface of a drum, that's the geometric shape
they occupy.
Well the set of all the same-numbered tracks on a stack of hard drive
platters also form a cylinder... I thought that was the reason.
--
_______ Shawn T. Rutledge / KB7PWD ecloud(a)bigfoot.com
(_ | |_) http://www.bigfoot.com/~ecloud kb7pwd(a)kb7pwd.ampr.org
__) | | \________________________________________________________________
Get money for spare CPU cycles at http://www.ProcessTree.com/?sponsor=5903
8:36 a.m.
At 09:37 AM 4/18/00 -0700, Shawn wrote:
Well the set of all the same-numbered tracks on a stack
of hard drive
platters also form a cylinder... I thought that was the reason.
My understanding of this, and I believe the source was Bill Joy when I was
over at Sun describing the Berkeley "Fast File System" is as follows:
Both John and Shawn are correct. The derivation of the term "cylinder" for
disk geometry descriptions came from the fact that in a multi-headed drive,
Track 'n' on all platters formed one cylinder. Given that disks had a hard
time seeking quickly, things that you could put on one cylinder could be
accessed like a drum without any head movement. In BSD they added "cylinder
groups" which were collections of cylinders (usually 3, sometimes 5) where
the heads need only move in our out one or two steps from the "home"
cylinder to get to a particular bit of data. Then by clustering data into
cylinder groups you could acheive higher disk throughput then if you put
things onto any old track.
--Chuck
9:22 a.m.
On Tue, Apr 18, 2000 at 10:36:20AM -0700, Chuck McManis wrote:
Track 'n' on all platters formed one cylinder.
Given that disks had a hard
time seeking quickly, things that you could put on one cylinder could be
accessed like a drum without any head movement. In BSD they added "cylinder
groups" which were collections of cylinders (usually 3, sometimes 5) where
the heads need only move in our out one or two steps from the "home"
cylinder to get to a particular bit of data. Then by clustering data into
cylinder groups you could acheive higher disk throughput then if you put
things onto any old track.
Somebody once told me that the definition of a "real pro" database admin
is somebody who can put the right tables on the right cylinders to
optimize throughput. But I didn't know it was an OS-level feature...
guess it would have to be.
--
_______ Shawn T. Rutledge / KB7PWD ecloud(a)bigfoot.com
(_ | |_) http://www.bigfoot.com/~ecloud kb7pwd(a)kb7pwd.ampr.org
__) | | \________________________________________________________________
Get money for spare CPU cycles at http://www.ProcessTree.com/?sponsor=5903
9:43 a.m.
Somebody once told me that the definition of a
"real pro" database admin
is somebody who can put the right tables on the right cylinders to
optimize throughput. But I didn't know it was an OS-level feature...
guess it would have to be.
people who do tu58 for VAX730 or RT11 on pdp11 know this trick well.
After all rewinding a tape for one file out of order can easily cost 20-30
seconds!
Allison
10:20 a.m.
New subject: test - please ignore
Test post to this newsgroup. Sorry for the intrusion.
1:58 p.m.
New subject: Looking for software/docs for MacADIOS 411 product
I recently picked up a really neat peripheral device for very early Macs.
Its labelled "MacADIOS model 411" and is a laboratory instrument interface
supporting both digital and analog inputs and outputs. It communicated via
the seral port of the mac (a 9-pin DIN, so you know it for early Macs!). At
its core is a 6502 cpu and looks to have been made around the mid 80's.
Problem is, I have no SOFTWARE or MANUALS for it. Can anyone help me out?
I've contacted the company that manufactured it (GW Instruments, Cambridge,
MA) and they have no information available on their old device and the best
I could get them to do is post a request on their lunchroom cork board.
I've gotten no response to that in over a month.
Thanks in advance,
John Lewczyk
12:42 p.m.
Every flight simulator I worked on in the late '60s to early '70s had these.
Just
before the advent of the mini-computer Link used to build their own computers,
24-bit, 20+cabinet beasties and used drums as main storage. Ours were not very
reliable, requiring resurfacing every couple of years. Several companies came
out with solid-stae replacements and most operators quickly jumped at these.
We still have one of these dinosaurs (minus the drum) but its going out the door
in two months. I won't miss it .... oops...guess thats blasphemous on this
list...
Will Jennings wrote:
Hi,
I think I heard somewhere that magnetic drums are somewhat like core memory,
i.e. they retain their contents when shut off... I believe I read this in
the IBM 704 manual, so I'm not entirely certain that facts about those drums
(8192 36-bit words!) can really be applied to the drums I'm going to be
getting, which are from Vermont Research and are approximately 256K or so..
Also, does anyone know what other computer companies used drums from Vermont
Research? They're for my Interdata 7/32, but I know at least Varian used
Vermont Research drums... any others?
Will J
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
19 Apr
19 Apr
3:48 p.m.
Will Jennings wrote:
Also, does anyone know what other computer companies
used drums from Vermont
Research? They're for my Interdata 7/32, but I know at least Varian used
Vermont Research drums... any others?
HP used VR drums as storage in the 2000B...
--
Chris Kennedy
chris(a)mainecoon.com
http://www.mainecoon.com
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13 comments
11 participants
participants (11)
-
allisonp＠world.std.com -
chris＠mainecoon.com -
cmcmanis＠mcmanis.com -
cube1＠home.com -
Hans.Franke＠mch20.sbs.de -
jlewczyk＠his.com -
John.Allain＠donnelley.infousa.com -
jpl15＠netcom.com -
oliv555＠arrl.net -
rutledge＠cx47646-a.phnx1.az.home.com -
xds_sigma7＠hotmail.com