I posted this over on the rescue list, but I figured it's probably close enough for here too, since I use these for classic machines. I'm looking for magneto-optical disk cartridges. Primarily the 3 1/2" versions, I use the 128mb disks for shuffleing data around between old machines, but I actually have a mix of drives - 128mb mostly, but also a 230mb and a 640mb drive. I also checked last might, and found the 600mb 5 1/4" drive I had forgotten about. Just no media for it.
I've been checking on eBay, and they turn up from time to time, and I actually just bought a few 128mb disks there. But mostly, the MO disks available tend to be the expensive, higher capacity disks that I can't use. These old, small ones rarely get listed, and I almost never see used ones. Or, when they do get listed, the shipping is wildly inflated. For example, I found an auction for 20 used 128mb disks. Flat rate $20 shipping. How it can possibly cost $20 to ship a small box of disks is beyond me. Likewise the BIN of $2 for five disks, with flat rate $12 shipping.
So, anyone have a good source of these critters? I remember buying a few boxes many years ago (back when the Zip drive was the great new thing) from an online media store, and paying about five bucks apiece for brand new 128mb cartridges. Surely the prices should have come down, but the the cheapest I can find them is $7 each. I'd really like to just buy some used cartridges, but I guess the used media market isn't what it was, I don't really even see used tapes much anymore.
So, anyone know of a source of 128mb, 230mb, 540mb or 640mb 3 1/2" disks, or the 600mb 5 1/4" disks?
-Ian
I have a brand new Cipher Model 920 9-track tape drive that needs a
new home. It can do either 800 or 1600 BPI and uses what I believe is
a Pertec like interface, i.e. Pertec compatible signals, but non-
standard connector pinouts. It also comes with a complete set of
documentation and schematics. From the picture below, you can see
that it is still in the original shipping frame with all of the
protective paper still on the plexiglass.
http://web.mac.com/mardy/iWeb/Cipher920/front.jpg
It was given to me for free by someone else on the list, so I'm going
to continue the tradition and offer it for free as well. For local
pickup, I am located in Southern New Hamphire, but I am also willing
to ship it if someone is willing to cover the shipping costs. I have
already crated it. I am guessing that it will be somewhere around
$150.00 to ship it within the continental US.
-Mardy
No
------Original Message------
From: Greg Manuel \(V\)
Sender: cctalk-bounces at classiccmp.org
To: General Discussion: On-Topic Posts Only
ReplyTo: General Discussion: On-Topic and Off-Topic Posts
Subject: RE: Datec?
Sent: Nov 9, 2008 4:15 AM
Evan, do you mean Datek? They were electronics liquidators. Well, they did
electronics and lots of other stuff to. It was a catalog(ue) company IIRC.
Greg
> -----Original Message-----
> From: cctech-bounces at classiccmp.org
> [mailto:cctech-bounces at classiccmp.org]On Behalf Of Evan Koblentz
> Sent: Thursday, November 06, 2008 11:31 PM
> To: 'General Discussion: On-Topic and Off-Topic Posts'
> Subject: Datec?
>
>
> Is anyone familiar with a company called Datec Inc., based in Colorado
> Springs in the mid-1980s?
>
I have a Quimax PX 22. I had it hooked up to my PC XT to a CGA card. It
was working but began to heat up so I shut it off. Tried to bring it up
using a A/C VARIAC. But nothing. It has the ability to display in Red or
Green or White. Is it worth fixing. Is anyone interested in IT. It might
be an easy fix Couple of CAPS.
Not too sure what I did with mine, but is cannot find
the activation Key info. I'm trying to get a old Wyse
LoadStar 286 Xenix box going and this version seems
to be able to handle the serial port as console. I can't
get any of the other versions I have to take the serial
port as console they all switch as they boot or error
when the run hardware tests.
Mine disks have a part number on it of 12866, not sure if this
means anything. (Xenix Sys V release 2.2 version 286AT)
The Wyse LoadStar is just a 286 PC with special ROMs. and no
Video card or Key board.
- Jerry
Here is part of an oral history I recorded with Steve Russel last
August which discusses how the Spacewar! program works internally.
Exerpt of an oral history of Steve Russell
August 2008
CHM Reference Number X4970.2008
(C) 2008 Computer History Museum
Russell: Anyway, the PDP-1 arrived, and Marvin Minsky wrote the tripos
demonstration, generally called the Minskytron, and there was the famous weekend
where the mob of undergraduates transcribed the macro assembler from TX-0 to the
PDP-1, because they didn't like FRAP. And then fairly quickly thereafter, they
wrote DDT and connected up the macro symbols to DDT. So that was all sort of in
place by the middle of the fall of 1961. And the combination of the Minskytron and
having DDT with interactive debugging with symbols was very tempting. I don't
remember the exact order of things, but I'm pretty sure I started talking up a better
demonstration program than the Minskytron, and eventually, Alan Kotok went up
to Maynard and collected the sine and cosine routines from DECUS, presented
them to me, and said, "Okay, here are the sine and cosine routines; now what's your
excuse?" And I discovered I had run out of excuses; I had to actually think. And so
I started work and figured out the basic trick of Spacewar! display which is that you
only need to calculate a unit vector pointing in the direction of the spaceship. And
you can express everything else the spaceship does, and the outline of the spaceship
in terms of that unit vector, suitably scaled. So it's basically a lot of addition in the
usual program upkeep.
Kossow: Do you want to just give an overview, then, of how Spacewar! actually
works?
Russell: It's one big loop, and the loop is on the displayable objects. And I called
them displayable objects, although I didn't know about object orientation or object-
oriented programming at the time.
Kossow: So you have the sun--
Russell: Colliding objects, not displayable objects. The colliding object is a space
ship, there are two of those. And that has a lot of extra data with it. It shares the
position and velocity tables with all of the torpedoes and explosions that are running
around. So there's just one big loop through the colliding objects, and it looks at all
the higher-numbered colliding objects to see if there's a collision, using an octagon
because you don't need to calculate the square root of anything, you can do that by
work on X difference, Y difference, and X+Y difference--
Kossow: So the bounding box for the collision detection is an octagon?
Russell: Yes. So it goes through, it sees if this object is colliding with any higher-
numbered object. If it is, it replaces the calculation routines. That's another thing
that every colliding object has, is a calculation routine. It replaces the calculation
routine with the explosion calculation routine. And then things take care of
themselves. Then, after it's decided whether it's an explosion or not, it goes off to
the calculation routine. And the calculation routine updates the position, since all
colliding objects have velocity; and if it's a spaceship, it worries about reading the
controls and updating the other things about the spaceship in deciding whether to
launch a torpedo or not. And if a torpedo needs to be launched, it searches up the
colliding object table for an empty slot, indicated by having no calculation routine.
It searches up the table for an empty slot, puts a torpedo calculation routine there,
and the spaceship position plus the suitable increments, so it won't run into its
torpedo, and of the velocity of the spaceship plus an increment for the torpedo, and
it goes on. When that the main loop gets done, you go off and do some star display
and display the sun, and calculate -- and part of the spaceship calculation is to
calculate the effect of gravity on the spaceship. Originally, there wasn't any gravity,
and I had an interpreter, which interpreted the outline description, and Dan
Edwards, sometime in late 1961 or early 1962, looked at that code and decided if he
could write a special purpose compiler which would compile precisely the right
code, and proceeded to. And there's one compiled outline for each spaceship; each
spaceship actually does half of the spaceship outline and then you twiddle the
vectors and do the other half. That keeps the display running just as fast as it can.
That gives time to calculate the effect of gravity on the two spaceships, but not on
the torpedoes. So we decided that they were photon torpedoes not affected by
gravity.
Kossow: So when the explosion routine starts, it continues calculating motion, so
the explosion moves?
Russell: Yes. If you see two spaceships collide, if you watch closely, you will see
that there are two explosions that continue off in the direction that the two
spaceships were going. There is another number in the table for all colliding
objects, which is the size. And this is, roughly speaking, proportional to the amount
of computing it takes to compute that object. And at the end of the loop, as you go
through the main loop, you accumulate the sizes also; and so at the end of the loop,
there's fritter away time loop that attempts to keep the frame rate approximately
constant. It doesn't do a wonderful job; it's visually adequate, but God help you
when you try to take a movie of it.
Kossow: One of the complaints with all modern kids trying to play it now is
that it's TOO SLOW.
Russell: Kids who are used to something like Asteroids seem to think that. But
when we do the demos, we get a number of people who seem to be still quite
addicted to it with the old, slow version. Now, that was always a complaint; the
reason that all the parameters got accumulated in the first page of the listing, which
says you can put that first page of the listing of the console, and anyone who wanted
to try a different set of parameters could. But the ones that were compiled in or
assembled in were the ones that I thought were good. Now it turns out I'm not a
representative arcade game player, and so my version of the parameters is slower
and gives more opportunity for marksmanship than the arcade version.
Kossow: Right, that's the whole thing with gravity and doing the, what's that called,
where you whip around the sun? Does it have a name, where you whip around the
sun and you shoot?
Russell: The closest name is the "CBS maneuver" is what happens when two lazy
experts fight each other, which is they both turn at right angles to the sun, and fire
for 3.5 or 4 seconds, so they're now in stable orbits, and they know it. And then they
turn at each other and start trying to place torpedoes where they think the other one
is going to be. And so the trails turn into an eye around the sun, and CBS used that
as a logo, so it got called the "CBS maneuver". You can-- one of the spaceships can
go the other way around the sun, so that both ships meet on the same side of the
sun. But that seems usually to have less chance of winning. Not much less, but
somewhat less.
Kossow: It's better that you stay on opposite sides, then?
Russell: Yes.
Kossow: And then at some point, you added hyperspace?
Russell: Yes, and we realized that that was going-- I don't remember whether we
actually had it. I may have had it for a little while with no limit, but it became very
clear that someone who didn't understand could use hyperspace to escape their
proper justice forever, and so we added the unreliability of hyperfield generators
very quickly. One thing that Asteroids and the arcade versions, the later arcade
versions of Spacewar! added, which actually was a big help, especially with their
high acceleration rates, was "training mode" where space was actually viscous. So
if you got your ship accelerated so that it was going across the screen so fast you
couldn't understand what was going on, if you took your hands off, the situation
would gradually become understandable. I don't think I would have been persuaded
to do that in the original Spacewar! because it was unrealistic. But it definitely
made it easier to learn.
Kossow: So are there any other favorite anecdotes about Spacewar!, or just the
spread of Spacewar!?
Russell: Well, the "imitation is the sincerest form of flattery"-- many people saw
Spacewar! as, some people ask for copies of the source, and of course we gave them
out because we very briefly considered trying to sell Spacewar!. We realized the
only possible customer was Digital Equipment, and we also, on a little reflection,
that they were too cheap to do it. So we gave it out to anyone who wanted it, and
some people got the listing and thought about it, and by reading it-- a lot of people
simply saw the game and had a computer that wasn't the PDP-1 but did have a
display, and implemented Spacewar! their own way. I suspect most of them figured
out the "basic trick", but I'm not sure.
Kossow: What "basic trick" were you thinking of?
Russell: That you could do everything based on the spaceship unit vector. How are
you fixed for the source code for different implementations of Spacewar!?
Kossow: We have a few. I don't know if we have the PDP-10 version. We have the
12 version, and I think we have a PDP-7 version.
Russell: I think Bob Saunders wrote the PDP-7 version. I think one 6 version
simply ran on the PDP-1 simulator. I think there must have been others, but I don't
know. Something for some history grad student to pursue. When we were running a
demo for the Yelp event, there was one woman who had done Spacewar! in turtle
graphics as a high school programming project, which she wasn't too happy with.
She seemed to like the demo of the original Spacewar!.
Kossow: So turtle graphics running on a micro or something like that?
Russell: I didn't quiz her. I didn't have the opportunity to quiz her further.
Kossow: So she thought this version was better?
Russell: No, she just thought it was nice to see the original.
Kossow: So she was in her mid-20s?
Russell: 20s or early 30s; probably 20s. The DEC field service story where the
DEC production people got into the practice of loading Spacewar! the last thing
before PDP-1 shipped, and field service would then unpack it, make sure that
nothing horrible had happened, tryed turning on power, and starting Spacewar!.
And if it worked, they would call the customer over and say, "See, it works." If it
didn't work, then they'd worry about it. In the restoration project, we had a little
reflection and we decided that probably if Spacewar! works, just about everything
works, as far as machine instructions go. It doesn't guarantee all the I/O gear works,
but it does multiply and divides, and just about every instruction. So a lot of people
implemented Spacewar! just from knowing that it existed and having seen it maybe
once.
Hi all,
I bet somebody has some documents from this toy.
I am starting to think about christmas, and all sorts of mechanical computers and toys.
One of the other fun computer tricks I recall, is using 3x5 cards. You can punch a row of holes in the top edge, and selectivley cut slots thru to the top.
So, a deck of cards with numbers on them, and appropriately cut slots, you can sort the deck with a pen, a binary sort by lifting the cards (its a bubble sort)
What other kid ideas do you guys have?
I'm going to bring a stepper controlled etch a sketch.
Randy
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