Brief notification, but I just heard a blurb announcing as per the subject
line, for those who happen to be near the radio in the next hour and can tune
in the CBC (after the news at 4).
(It's on the show "SPARK", if one wishes to try to hear a repeat.)
It is about the mainframe computer, but that's all I got ... can't testify
further as to the content.
Date: Sat, 15 Dec 2007 17:53:16 -0800
From: dwight elvey <dkelvey at hotmail.com>
Subject: RE: Quick survey
<snip>
>Hi
> There is nothing in the drive that is specific to the number
>of sectors.
-------
Except that a number of "modern" drives will not go ready and
pass data with any hard sector disks.
------
> The following were 10 sector disk:
>Polymorphic 8813 Used both single and double density disk
>H8/89 H17 controller used single density
>NorthStar single density ( double?? don't think so )
> These are all 5.25inch. As far as I know, 10 sectored was
>the most common. I don't know of any that used 16 sectored
>and never heard of 9 sectored.
>Dwight
--------
Just goes to show ya: all I've got are 16 sector disks, originally used
in CBM computers (not because they were needed but because they
were cheap) and now handy for my Vector Graphic MZs.
I think Jerome was talking about 9 sector soft sector disks.
mike
As an expert in this area, my opinion is that silicon sensors have a long ways to catch up to film. Both CCD and CMOS sensors lack in resolution and the spatial sampling artifacts Der Mouse mentioned are only part of the problem. (CFA array, metal shading of the cell) The world however, is focused (hahah pun intended) on the megapixel wars. Far more important is the geometry of the color filter array and conductors at the periphery, causing viginetting. Also, the conversion of the A/D in both systems is only 12 bits, far below the dynamic range of film and the eye.
While at Micron, we developed a high dynamic range sensor for the security camera market, by varying the cell precharge and a sub ranging A/D for the sample. Imagine a security camera viewing a dark face in the lobby, and the security cam looking outside the front door glass at the daylight street too, we could image both of these simultaneously, no f stop changes...
Lucas Film Pioneered the OpenEXR high dynamic range format:
http://www.openexr.com/
Also take a look at where film is with the Gigapixel project:
http://www.gigapxl.org/
Film has a few miles left for sure.
Randy
> From: mouse at rodents.montreal.qc.ca
> Date: Sun, 16 Dec 2007 11:03:30 -0500
> To: cctalk at classiccmp.org
> Subject: Re: digital camera capabilities / was Re: 1000+ old computer in
>
> > The effective resolution of 35mm film is IIRC considered by
> > professionals to be in the 27MP range; DSLRs are rapidly approaching
> > this.
>
> Perhaps - but film still has attributes which digital cameras don't,
> such as lack of aliasing artifacts (because the grains are randomly
> dispersed in the film instead of being in a neat rectlinear grid).
>
> /~\ The ASCII der Mouse
> \ / Ribbon Campaign
> X Against HTML mouse at rodents.montreal.qc.ca
> / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B
_________________________________________________________________
Don't get caught with egg on your face. Play Chicktionary!
http://club.live.com/chicktionary.aspx?icid=chick_wlhmtextlink1_dec
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
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
Your target of the technology of 1963 fits reasonably well with my
1962 mainframe, it uses drum(s) for backing storage (holding program
and data overlays to be brought into core) but I don't think that
makes much difference to the drum itself, other than you may want
more than one read/write head per track.
Each drum looks to be about a foot diameter and about a foot and a
half long. They spin at 5240 rpm on a vertical axis. The drum is made
of aluminium and the manufacturers (International Computers and
Tabulators) had a lot of trouble getting the surface coating right,
trying all sorts of high tech methods until they found the most
effective method was for someone to smooth it on by hand while the
drum was spun at low speed, rather like a potter throwing a clay pot.
They also had problems with the length of the drum, and had to
logically divide it into two sections, each one with its own timing
track and datum track. Hopefully if you keep the drum length small
this will not be a problem for you.
The drums are powered by 3/4 horse three phase motors with V-belts
providing a step UP in speed from just under 3000rpm at the motor to
5240rpm.
They do not need clean room conditions, they are not sealed, and even
have a fan to draw cold air up from the bottom over the surface and
out the top, or is it the other way around, I can't remember, the fan
are currently removed anyway and the drums run fine in a rural
environment (i.e. reasonably clean air, no coal fire smoke/smog/
diesel particulates)
The drum sits within an aluminium casing which holds 244 (+some
spares) read/write heads arranged in a helix so they do not need to
be physically close to each other.
The heads do not fly, and can be moved in and out using an Allen key,
which is apparently done whilst watching a pressure gauge on an
airline blowing air through a venturi in the read/write head, so that
when the air pressure reaches a certain level, the head must be close
enough to the drum because the drum is starting to impede the air
flow. The steel screws have now rusted and seized in the aluminium
but work just fine because if can't work loose they can't go out of
adjustment.
The drum is coated rather than plated, I know this because when
certain machines used by the Home Office for security purposes were
decommissioned, a friend of mine was required to dismantle the drums
and wash the magnetic coating off of the drums before they (the
drums) were allowed to leave the premises. The machines had earlier
survived being blown up by terrorists detonating a bomb on the window
ledge outside one of the computer room windows. They don't make them
like that any more, tough as old boots!
The same friend also worked on a serial drum machine with valves
which was installed at a Carbon factory where the inside of the
machine used to get covered in conductive fine carbon dust. It is
amazing it worked at all. Another friend worked on modern electronic
weighing equipment at a phosphate factory using bird droppings as the
raw material. He was called in to one machine which had stopped
working the previous day, and found a small rubber grommet had
failed, the chemicals had got in and eaten the resin of the PCBs and
the copper tracking was hanging loose inside the cabinet, it seemed
that it had somehow been working in that state for some time because
it would have taken some weeks for the resin to be consumed, so maybe
this contradicts my statement that they don't make them like that any
more.
The 1MHz main machine clock is derived from the 250KHz drum timing
track, so no need to synchronise to the drum except when switching
between drums, or the two halves of a drum.
The machine can also be run from a separate clock, though of course
all drum accesses fail. For fault finding, it can even be run one
cycle for every time you press a button, wonderful to watch data
shifting through the registers displayed on the front console and see
where your data is getting corrupted. Not so good for fault finding
the drum, magnetic tape or other peripherals though.
I hope some small part of these details might be of help to you, good
luck with the project.
>
>Subject: Re: KayPro II keyboard schematic?
> From: ard at p850ug1.demon.co.uk (Tony Duell)
> Date: Sat, 15 Dec 2007 23:09:21 +0000 (GMT)
> To: cctalk at classiccmp.org
>
>> It has an 8048 uP if memory serves and the output is TTL level serial
>> ASCII. Making it put out parallel would be a major hackup including
>> reprogramming an 8748.
>
>Or alternatively converting that serial output to parallel using an
>external circuit. How hard that is depends on the format of the serial
>data. If it's an asynchonous signal, with start and stop bits, a 40 pin
>dumb UART chip should do it.
>
>What was used inside the Kaypro to receive the keyboard data?
Z80 DART, The keyboard is a simple TTL level serial (async)
protocal. It's bidirectional for lighting leds if memory serves.
Allison
>
>-tony
>
>Subject: Re: Homebrew Drum Computer
> From: Gordon JC Pearce <gordonjcp at gjcp.net>
> Date: Fri, 14 Dec 2007 10:01:09 +0000
> To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
>
>On Thursday 13 December 2007 07:48:00 Robert Nansel wrote:
>
>> Certainly I could trash a few old cassette decks, or even get some
>> floppy R/W heads to experiment with audio recording tape super-glued
>> to a soda can, but I really want to get at least the performance the
>> old machines could produce, so that means a reasonably fast drum RPM,
>> somewhere around 6000 RPM, say.
>
>That's actually pretty fast, and anything you stick to the drum will need to
>be stuck very firmly! By comparison, a washing machine in fast spin goes at
>roughly a quarter of this speed, and a typical car engine is reaching
>its "red line" at around 6000rpm...
>
>You would need an extremely good workshop to machine up a drum that would stay
>in balance at this sort of speed. It's actually the sort of thing that you
>might want to farm out to a specialist machine shop. I would be inclined to
>make the drum out of a bit of thick-walled aluminium tubing, carefully bored
>to remove any imperfections from the inside that might affect the balance. A
>couple of aluminium end caps would take a thickish steel axle and the
>bearings (which would be tricky in themselves - they'd need to be sealed to
>prevent grease being thrown out, or something capable of running fairly dry
>at high speed). Then you'd skim the drum to ensure it was perfectly
>concentric - any runout would very quickly destroy the bearings at 6000rpm.
>Some motors use little sealed ball races. I'd consider looking at teeny-tiny
>taper roller bearings like car wheel bearings, so that you could use a shim
>to set the preload very accurately to remove any play. I can probably
>provide a scan of a car gearbox manual that shows *exactly* how to do this
>bit.
>
>You'd probably need to balance it after painting or otherwise coating it with
>some sort of magnetic material. I don't know what you'd use for that. You
>could probably research what they used in early drives. I am now entering
>the realms of speculation, but my gut feeling is that you'd need to somehow
>spray it on and rub back the layers to get a perfectly smooth finish - when
>it's done it shouldn't quite be hot-rod shiny but it should be very flat and
>polished.
>
>Over to Tony, I think...
Most of the old Drum machines spun at 1200, 1800, 3125 or maybe a screamigly
fast 3600. Though 1800 is the more common.
Also most used "fast tracks" that had more than one head per track
radially so that a partial rotataion was needed.
A good machine to study is the Minuteman Missle guidence computer. It
was bit serial and used a disk as a "drum" rotating memory.
Allison
Allison
>Gordon
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 you
