Date: Sat, 15 Dec 2007 13:23:13 +1030
From: Robert Nansel <bnansel at bigpond.net.au>
Subject: Homebrew Drum Computer
>I thought of this, too. So far I haven't found an online source of
>them (Google search terms: "glass delay line" OR "quartz delay line"
>OR "ultrasonic delay line" TV PAL OR NTSC).
>-Bobby
Fri Dec 14 19:10 Tony Duell wrote:
>> I wonder if you could use those glass delay lines that were used in
>> PAL colour TV receiver until fairly recently (and there must be plenty
>> still around)? Alas they have a somewhat odd delay time (a little less
>> than 64us -- one line period of the European TV signal), but I am sure
-----------------------
I've got some old VCR boards with 2 glass delay lines on 'em:
Markings: DL BTB85B 042 (Component # DL2K0, 6cm long, 4 pins)
And: ADL-FN2038M 337P16301 4003 (DL6A0, 3cm, 3 pins)
Just slabs of quartz with wires attached (the covers are removeable).
Might be tricky to find specs though; unfortunately no idea of the VCR
make/model.
Also should have an old MS delay line somewhere.
mike
On 15 Dec 2007 at Robert Nansel <bnansel at bigpond.net.au>:
> * Delay lines: I have a junk magnetostrictive DL on the way. I
> don't know if it works.
Golly, if you're talking about producing your own drum, a
magnetostrictive delay line would seem to be like a walk in the park.
Find some nickel wire; make a large-looped coil with the turns
supported by something like neoprene spacers so that they're
mechanically isolated; put a coil on each end. Shock-mount the whole
affair in a box.
The Packard-Bell 250 was a great little machine along the lines that
you're contemplating. Used delay-line memory and had a 22-bit word.
You could plug it into a 115-volt wall outlet. Few transistors and
lots of diodes, IIRC. Really one of the earliest minicomputers
around. There are several that are extant. I recall seeing the
memory in a 250 and being surprised at its simplicity.
> I was thinking I would implement a data stack and a return stack,
> each being made of short recirculating buffers to hold the top two or
> three stack entries, with the older entries swapped to longer buffers
> with corresponding longer access times. Allowing for the overall
> insanity level of this project, is this seem a sane strategy?
Sounds pretty complicated to me. Why not a simple one-plus-one
architecture? It may not be fast, but then, no drum- or delay-line-
based machine is going to be a speed demon...
Cheers,
Chuck
Would I be more-or-less correct if I assumed that the bulk of hard-
sectored diskettes in use fell into two groups: 16-sector 5.25" and
32-sector 8"? I know that there are other physical formats, but I'm
wondering if that would have 90% coverage?
Thanks,
Chuck
-----REPLY-----
Chuck,
If I were to pick two of the most common, I would pick 10 sector 5.25" hard
sector floppy disks and the 32 sector 8" hard sector floppy disks. There is
a less common 16 sector 5.25" hard sector floppy disk as well used on Vector
Graphic, AES, Exidy Sorceror, and a few other exotic platforms.
Of course, none of the hard sector media are exactly common...
[drifting slightly off thread but in a related manner]
BTW, I did get Catweasel Vector Graphic working. I am in testing now and
will be changing the output format to support the simulator work underway
presently. Nothing major; just time consuming and the usual stuff.
My Catweasel programs seem to work fine but are not really designed for easy
modification. Quick hacks rarely are. It turns out to be major oversight
though; there are even more diverse and incompatible disk formats for VG
than for NorthStar or Heath which is really saying something.
The frakkin' hard sector disk formats are just crazy in the ways things vary
>from one vendor to the next and even within different OS's from the same
vendor. "No rules for hard sector disks" is a profound understatement!
Thanks!
Andrew Lynch
Apple I is Vince's deal -- www. brielcomputing.com (or maybe it is "brielcomputers.com" or something like that...)
-----Original Message-----
From: "Matt Lichtenberg" <kerobaros at gmail.com>
Subj: Small SBC kits for Christmas!
Date: Sat Dec 15, 2007 9:23 am
Size: 918 bytes
To: cctalk at classiccmp.org
So, every year I like to get myself a little something; this year, I'm
probably going to be getting a new computer (outside the realms of
this list), but I'd also like to get some kind of single-board kit
that I can work on.
I'd like something along the lines of a ZX-81 kit, although it looks
like those are selling for somewhere around $250, when you can find
one. SpareTimeGizmos' Elf 2000 kit also looks fantastic, but I don't
have an 1802 or an 1861 to use in the thing, and I'd rather not hunt
any down. (If anyone wants to get rid of theirs, though, let me know.
*grin*)
Has anyone seen any similar kits out there? They don't have to be
useful for anything, just fun to play with, and not horribly difficult
to put together. I can solder fairly well, and I'm mean with a
multimeter, but I don't have the money for my own oscilloscope; I just
use other peoples' when they're not looking. Thanks, folks!
~Matt
The SDS9300 I used to service had a drum memory, unfortunatley can't
remember the type but I do recall that the drum was slightly tapered and
had a rising bearing assembly. As the drum finally ran up to speed it rose
an amount to bring the heads to the correct position and gap.
Basically a "parking" system, when stopped the drum had dropped, so the
heads were not at their working position. Heads were adjusted for position
with the drum stopped using gauges, so as it was stopped and down you did
not risk damaging the track. Spin it up to speed and the heads
automatically got to the tracks and flying height.
I recall it being about 2ft in diameter and about 4ft tall took about 30
seconds to come to speed and had its own motor generator set as it ran on
a dedicated 60 cycle supply not the usual 50 we have here in the UK. I
think it had 4 banks of 24 heads in fixed position. It was the one bit of
kit we did not touch, a specialist used to fly in from the US once a year
to check it and rewrite the timing tracks.
Mike
Al,
A while back you asked for the Versaplot sources, I have them here with a port to the PC DOS (Ryan-Mcfarland Fortran).
I also found them on the web:
http://history.dcs.ed.ac.uk/archive/apps/edwin/randomvms/
A google of versaplot turned this up, and also some manuals in what looks like troff format.
It looks like all the DECUS stuff is out there itoo f you google a bit.
I would like to see your MOVIE.BYU!
Randy
_________________________________________________________________
i?m is proud to present Cause Effect, a series about real people making a difference.
http://im.live.com/Messenger/IM/MTV/?source=text_Cause_Effect
Date: Fri, 14 Dec 2007 14:52:29 -0800
From: "Rick Bensene" <rickb at bensene.com>
> Some of the smaller drum-based computers from the late '50's and earlu
> '60's (transistorized) had drums that didn't rotate nearly as fast as
> 6000 RPM.
I don't know--the drum on the IBM 650 spun at 12,500 RPM, was 4
inches in diameter and about a foot long.
This is not a project I'd launch into lightly. In the 70's and 80's
Meshna would occasionally offer a mil-surplus drum unit for sale
usually from some some airborne installation (i.e. used in radar).
Lots of heads and no guarantee.
The precision necessary in the mechanicals is pretty daunting. The
heads fly at a few micrometers above the surface of the drum, which
pretty much mandates some sort of clean-room environment. The
bearings would need close to zero runout and getting the surface of
the drum coated smoothly enough, either by plating or with a magnetic
emulsion would also be an obstacle.
If you have a good precision machine shop and mechanical engineering
skills at your disposal, you could try it.
Personally, I'd rather work something up with a magnetostrictive
delay line memory--easier to build and quite robust--and just as
"vintage".
I recall that even in the 70's, drums had their problems. On the CDC
STAR, every so often, a station would go down because of a "drum
error"--more frequently than the disk drives encountered errors. You
could make the heads on a Univac Fastrand II drum "ping" just by
jumping up and down on the floor near the monster. I also recall
that the ADL folks at CDC were working on a "super drum"--a very high
speed unit that spun in a vacuum(IIRC) to be used as a paging store
for the STAR. I recall the Neil Lincoln mentioned that the time
between the observation window being clear and coated with drum
surface was typically a few minutes at best.
There's a nice story about the Manchester Mark I drum here:
http://www.computer50.org/mark1/gethomas/manchester_drums.html
About the only item of the correct size and tolerances that's readily
available today, it seems to me, would be the drum unit out of a
laser printer or copier. I don't know if the OPC layer could be
easily stripped off and replaced with oxide, but it might be worth a
try.
If you're really serious abou this, I'd be willing to donate a head
>from a CDC 808 disk unit--4 bit parallel recording.
Cheers,
Chuck
Date: Thu, 13 Dec 2007 21:55:51 -0500
From: "Andrew Lynch" <lynchaj at yahoo.com>
Subject: KayPro II keyboard schematic?
>Hi,
>I recently bought a KayPro II keyboard. It contains a nice Keytronics
>mechanical keyboard and really nice case. I'd like to convert it to a
>parallel ASCII keyboard or just reuse its case but was wondering if anyone
>had the schematics?
>Please let me know if you have the KapPro II keyboard schematics. Thanks!
>Andrew Lynch
-------------
How about leaving the keyboard intact and just adding a simple serial>parallel
converter between it and the VG box? Add an EPROM for code conversion
if necessary.
I've got some serial interface cards for Olivetti typewriters (with schematics) that
you could probably hack fairly easily if you didn't want to start from scratch; even
FIFO buffers for typeahead, although you wouldn't need that with a Vector.
mike
>
>Subject: Re: Homebrew Drum Computer
> From: Gordon JC Pearce <gordonjcp at gjcp.net>
> Date: Fri, 14 Dec 2007 14:42:34 +0000
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On Friday 14 December 2007 14:19:06 Jules Richardson wrote:
>
>> Very interesting project. Won't standard tape heads only work reliably if
>> the magnetic material's passing by at quite a narrow range of speeds,
>> though? Google suggests that's 1 7/8" per second, which isn't very fast at
>> all - a drum that can do a few tens of RPM seems possible, but 6000??
>
>I don't think it makes a difference. The higher the speed, the larger the
>voltage from the flux transition, but that shouldn't be a problem (within
>reason). The head gap and medium speed dictates the "resolution" of the
>system. You can think of it as being like trying to write with different
>sizes of pen nib.
>
>Look at reel-to-reel audio recorders - they may run at a variety of speeds,
>giving a tradeoff between audio quality and recording time. You can use a
>higher flux density with a larger head gap (and a correspondingly larger
>drive signal), but you need to haul the tape through faster to maintain the
>bandwidth.
However the inductance of the head windings are a significant factor in
how high you can go for bandwidth.
>On playback, you get the problem that higher frequencies produce a higher
>voltage, hence the need for equalisation (not unlike the RIAA curve for
>magnetic record pickups).
>
>In this case you probably just want to detect the presence or absence (or
>possibly polarity) of a pulse. Equalisation won't be a worry.
At low bit densities it's not an issue otherwise you get into peak shift.
Low being around 300FCPI (Flux Changes Per Inch) based on testing I did
30 years ago. I was using the best ferrite heads I could get my hands on
>from top of the line analog casette decks. Those heads were very limited
and heads from 1/4" machines performed far better and still limited me
to under 600FCPI at 15ips (~4800 bits sec) for NRZI and I could hit 9.6k
using phase encoding. Most audio heads are not so hot for saturation
work.
Allison
>Gordon
