><Anyway, so I wired up my #2 nut with sense wire to the h-bridge and start
><slapping current back and forth through my nuts. :-) Seriously though when
><viewed on 'scope it looks something like:
><
>< +--+
>< | |
><Ch1 -+ +----+ +-----
>< | |
>< +--+
>< +--+
><Ch2 -+ +----+ +-----
>< +--+
>
> Transformer action prior to saturation.
>
><UNTIL you get to about 7.5 amps or so, and then it looks like:
>
> No you know what nuts dont work...
I don't usually have trouble with American English, but I must confess this
baffles me. Does it mean something like "Now you know why nuts don't work"? :-)
>< +--+
>< | |
><Ch1 -+ +----+ +-----
>< | |
>< +--+
>< +--+
><Ch2 ---+ +----+ +-----
>< +--+
><
><So I stared at it a bit and the little bulb went on between my ears.
[snip]
> Yep. Watching that spring snap in interesting on a scope. Those nuts are
> slow too! Try a bunch of other materials now that your set up...
Hows this for an idea. If you find that the toroidal ferrites that Siemens and
people make don't have enough hysteresis, why not go to the other extreme and
try the stuff magnets are made of. Ring magnets as used for loudspeakers and
things are probably a bit large :-) - I wonder if it's possible to drill a
hole down a bar magnet and then cut slices off. For mass production, I'm sure
the magnet manufacturers would sell you the stuff unmagnetised...
><The gap between the pulse start and the sense pulse is used to tell whethe
><or not the core had a 1 in it. Now in the DEC design what happens after th
><read pulse (which is really a "write zeros" pulse, is they take the data
><they just read and re write with the write ones pulse. However this time
><since the sense lines aren't needed to figure out what the cores had in
><them, they use them for "inhibit" currents.
Now can someone enlighten me: There will be a minor glitch-type delay between
read and sense pulses with no transition, and a much bigger delay with a
transition. How do you tell the difference? Is this one of the applications
where a monostable really is useful?
><Cool stuff, now it raises some new questions:
>< 1) Do you want your pulses to be long enough to switch the
>< core exactly, or longer? (eg does writing a zero just cancel
>< a one or does it cancel the one and write a zero in its place?)
>
> I forget.
Perhaps now you have a test rig you can try different pulse widths as well...
>< 2) Why not just gate the write one current pulse? That would save
>< on the inhibit current stuff.
>
> well you have to know what your writing back and to do that you have to
> read it first. Hence the common write after read cycle on many machines
> from the era of core.
I think what he meant was: Rather than sending write current through all core
planes and inhibit current back through those to which you don't want to write,
why not send write current only through those planes to which you want to write?
My initial guess was that you might connect the write wires of several planes in
series, and have a single driver for the lot.
But then I realised that this would be very difficult to drive - the voltage
required to drive a given current would depend on what you were writing - or
worse still, what you were reading!
So why is it done this way?
>< 3) What properties of a material make it easier to switch at lower
>< currents? I don't want to build a core plane with nuts if I need
>< 8 amps to switch them.
>
> Good magnetic conductors that hold their magnetizm. Some steels, ferrites,
> cobalt alloys, alnico, a few rare earths. Try some of those ferrite beads
> used for bypassing in RF work.
The other property that affects this is size. The smaller the core, the less
current it takes to magnetise it.
Philip.
On 27 Apr 99 at 23:33, Mike Ford wrote:
> **** RARE ***** ISA card, will trade for small plane or country
>
> I don't want to be the reason some poor guy out in the world stops using a
> piece of equipment due to the cost of some critical part that I have. OTOH
> if there are TWO such people needing the item, I see no reason why the one
> that "needs" it the most doesn't get it.
>
> BTW the card is a HP 48L REV A 88290-66501, the fingers look ISA to me, the
> connector looks DB25F, and the label on the bracket says Scanjet I/F card.
>
> What exactly is this, just a scanner controller card?
<CRAWLS OUT FROM UNDER DESK> Yes, I have one of these too I guess.
This is labelled C2502-66500 REV B 1994. The date sounds about right
as I remember ordering it. Mine has a bar code label with the
marking 4HE3PFG. From the documentation, ISTR that it is just a
barebones SCSI card that is designed to just about work with
an HP Scanjet. The SCSI Scanjet will also work with a proper SCSI
card so not having one is no great loss.
<\CRAWLS OUT FROM UNDER DESK>
Phil
**************************************************************
Phil Beesley -- Computer Officer -- Distributed Systems Suppport
University of Leicester
Tel (0)116 252-2231
E-Mail pb14(a)le.ac.uk
If you've got enough of these that they're not too valuable to ship into the
ether, I'd appreciate one of these documentation sets re: NT4.0.
Do you think they'd fit in one of those freebie USPS Priority Mail boxes and
within the 2-lb limit. If so, I'd be happy to send you a fiver for your
postage and trouble. The postage for a package of <2# is $3.20.
regards,
Dick
-----Original Message-----
From: Lawrence LeMay <lemay(a)cs.umn.edu>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Tuesday, April 27, 1999 3:33 PM
Subject: Re: When stuff has to go
<snip>
> I have all these Microsoft manuals and CD's for learning about Microsoft
NT 4.0
> (mainly administration stuff)... What i'm gonna do with 8-10 sets of this
stuff is
> puzzling me to no end.
>
>-Lawrence LeMay
The story doesn't give any idea of what CPU the machine will be based upon.
Anyone have an idea? ARM by any chance? A hacked version of NetBSD runs on
ARM already.
Kevin
At 09:48 AM 28/04/99 -0500, you wrote:
>
>Looks like Clive Sinclair is working on another portable, this time with
Linux
>and a non-Intel CPU.
>
>http://webserv.vnunet.com/www_user/plsql/pkg_vnu_template.comp_news?p_to_da
te=28-APR-99&p_cat_id=59&p_story_id=82266
>
>--
>David Wollmann
>DST / DST Data Conversion
>http://www.ibmhelp.com/
>
>
>
>
==========================================================
Sgt. Kevin McQuiggin, Vancouver Police Department
E-Comm Project (604) 215-5095; Cell: (604) 868-0544
Email: mcquiggi(a)sfu.ca
ok, tonight's stupid vax trick is deciphering the wonderous boot messages.
I've gotten the SPX card I was supposed to have, and things are looking
much better now than they had been before.
But (always the 'but'!)
The boot fails in an entirely different manner now.
Tests A, 3, and 2 give a '_' result which as I understand means whatever
it was testing wasn't found to test.
Test 1 gives a '?' and I get this message:
? 6 80A1 0000.4001
?? 1 00C0 0011.700E
>>> continue
?24 UNXINT 00010000 041F0000 01C
and then nothing more.
If I run the proper 'show' command (forgot which one I used) the disks
spin up (RZ23 and RZ24), and 'show boot' indicates it wants to boot from
the RZ24.
Help! I really do not know what I'm doing. (:
ok
r.
--- Cameron Kaiser <ckaiser(a)oa.ptloma.edu> wrote:
> [C= 1520 plotter]
> ::Does anyone out there have any software for it? (I don't recall seeing
> ::any on ftp.funet.fi).
>
> As a matter of fact, *I* do. Do you get comp.binaries.cbm?
Yes, but I don't check it as frequently as I used to (not your fault...
I don't have telnet access to my primary news server from where I am).
-ethan
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com
It would be well to get the timelines aligned. The model 1 was of 1977
vintage. The model -3 was worked up in the late '70's before Apple got its
juggernaut rolling. Radio Shack had a real chance to make the microcomputer
market its own. No one had a decent sales and service network, not to
suggest that Radio Shack's was really decent, but at least it was there.
The Model 3 was out in '81? by which time double density was "old hat" and
by 1982-1983, Apple had the door closed. Having turned out two (if not
more) pieces of relative rubbish, the RS people had no chance after 1983.
IBM was gaining acceptance (nobody ever got fired for buying IBM, right?)
and ultimately legitimized the PC for "respectable" business use. By mid
'84, the 8-bitters were in the "Komputerdaemmerung."
Dick
-----Original Message-----
From: Allison J Parent <allisonp(a)world.std.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Friday, April 09, 1999 5:09 PM
Subject: Re: What if,... early PCs (was: stepping machanism
><The RCA TV set design that RS used for a monitor for the model 1 was NOT
><really adequate for 80x24 display. (YES, I've done it.)
>
>It could but the opto isolator used to keep the hot chassis and the video
>seperate wasn't up to the task. Bypassed and of course using an isolation
>transformer it was much crisper even at 80 cols.
>
><Double density was NOT readily achievable in 1978. And the poor quality
>
>My dog, don't tell DEC that or intel.
>
><> was SLOW. The Z-80-card in the Apple was significantly (and noticeably)
><> faster. The two machines otherwise occupied about the same desk space,
a
>
>Than the TRS80, every thing was faster. Next to my S100 CPM crate with a
>real 4mhz z80 and no wait state memory they were both slow.
>
><> aside from the stupid, Stupid, STUPID choice to leave the Tandy machine'
><> display at 16 lines of 64 characters (about half of what was on a 24x80,
>
>As it works 64wide was more useful for word processing than 32 or 40.
>
>Allison
>
>> The one Mike has is definately the proprietary one (I also have one sitting
>> here). It was packed with scanners like the ScanJet Plus.
>
> If that one is rare then the MCA version I use with the scanjet I have
> must be unique! ;)
On the contrary, I have a scanjet (which I've never used) and the MCA adapter.
I have no machines with MCA, though (yet!), so I might be offering to buy the
ISA version. One day...
Philip.
NOS! RARE!! VALUABLE!!! (yeah, right...)
In the boxes from a recent acqusition, I found a number of boxed of
Centronics 'Linewriter' 400/800 and 1200 series ribbon cartridges.
Since I don't have any of these printers in the collection (in fact, have
never heard of the thing!), they are available to anyone who can use them
for cost of shipping or flat out free if you pick them up!
There are about six boxes (of six carts each) of the 400/800 ribbons, and
one box of the 1200 ribbons.
Of course, if you want to offer something interesting in trade, thats cool
as well! B^}
-jim
---
jimw(a)computergarage.org
The Computer Garage - http://www.computergarage.org
Computer Garage Fax - (503) 646-0174
>>> Coming soon to www.computergarage.org - the CBBS/NW on-line archives
>>> Coming to VCF III (2-3 October 1999) - CBBS/NW live!
[Power supplies with earth return]
> I have never looked but I suppose it might. I have a 400A service and
> sometimes I do a fair job of loading it. The transformer ped is out of the
Another difference! It is very unusual in the UK to give a domestic customer
more than 100A in the main incoming fuse. 400A on each side of your 115-0-115
supply is getting on for 100kW. Do you really use that? I would have thought
10kW would be more likely (my parents use 36kW at the winter peak, mostly
heating load. 50A from each of three phases at 240V)
Anyway, 400A on the 240V side corresponds to nearly 7A to be returned through
the earth at 14kV. Ouch! I wonder what the resistance of the earth connection
is. There will be a minimum resistance to prevent undue voltage rise under
short circuit conditions, but I don't know how this relates to earth return
circuits...
The only places where I've seen this sort of arrangement, there are still 2
conductors. One insulated to HV for the line, and one lightly insulated for the
(HV) neutral.
> way so I rarely go closer than 30 feet from it. They also must put the
> ground rod(s) inside the for safety (hate to think what it would be like if
ISTR that in the UK there is a minimum distance between LV and HV earth
electrodes.
> the ground got cut on the primary). I have never seen them but they have to
> be there somewhere.
Earth open circuit? Hmm. The entire HV winding rises to 13kV and the HV
neutral flashes over to the transformer tank? Assuming the tank is part of the
LV earth system. Otherwise the transformer tank rises too, and flashes over to
your house supply...
Philip.
