The reason is that if the cord runs through the whole IMSAI, a problem
can cause a whole lot more damage. Also, if there is a problem with
insulation, you are a lot more likely to electrocute yourself by
touching a switch in the front than in the back.
>Why not? I powered-up through the front panel, but with the
>front-panel removed from the backplane.
>-- Doug
>Using IMSAIs since 1998 :-)
>
>
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>> So can any of you recommend a good book on how transputers work in a
>> broad sense? I occasionally have the urge to take all the old PC system
>> boards lying around and construct some form of transputer system - ok,
>> so it's impractical, would be a lot of work, and wouldn't be of any
>> benefit at all, but it would be an interesting exercise :)
>
>> A transputer is a specific type of processor from inmos (IIRC), so you
you learn something new every day (or in my case, several hundred things
;)
I always thought that transputer was a general term for any processing
component in a parallel system.
>> However, you could certainly build a parallel processing supercomputer
>> from a bunch of old PCs. In fact, that was the original idea behind Cal
>> Tech's Cosmic Cube which eventually led to Intel's hypercubes (such as the
>> iPSC/1).
hmm, wait for Java chips to really take off and write the whole lot in
Java... now there's a plan... :*)
>
>> I wouldn't be surpised if somebody still has the Cosmic Cube code around,
>> which would allow you to network some 8088-based machines to create a
>> hypercube. I have an old Unix-based hypercube simulator from Intel which
>> was based on the Cosmic Cube code, but I haven't looked into the copyright
>> issues.
parallel systems was a whole area that I never got too heavily in to at
university and regretted it afterwards (and being a fairly specialist
area it probably means you can get away from bad products produced by
monopolising companies :^)
I was tempted to ask how fast these 8088-based 'cubes were, but I
suppose it's really hard to describe real-world performance of such
systems without actually using them...
Jules
>
What exactly is a transputer and how is it different from a normal CPU?
>A transputer is a specific type of processor from inmos (IIRC), so you
>wouldn't be able to easily make one from bits of other computers
How many processors were in the Cosmic Cube? What kind of speeds did it
reach? There was once a Circuit Cellar article on building a parallel
processing computer out of a 286 and IIRC from 16 to 256
microcontrollers. All that could do was calculate the mandelbrot set,
though, at speed reachable by an i486 (yes, I know that's not the
point).
>In fact, that was the original idea behind Cal
>Tech's Cosmic Cube which eventually led to Intel's hypercubes (such as
the
>iPSC/1).
>
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>>Doing it in transistors wouldn't be the same :-)
I assume that with enough picking and matching it is possible, _in
theory_, to build a similar circuit by replacing vacuum tubes with
transistors, i.e. it's just a matter of taste in your case.
>>
>>-tony
>>
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Tony Duell quoted me as having written:
>> battery - 12V was all that was left after voltage drop when the 30mA or
>
> Don't forget the few volts (probably 10V or so) dropped across the line relay
> coils at the exchange to sense the off-hook condition. The system is
> (obviously) designed so that a short on the line (no matter how short the
> line is) won't cause damage. Applying 'battery' straight to a line wouldn't
> allow for this.
Good point.
>> had to go the several miles to your house and back. May still be like
>> that, come to think of it.
>
> AFAIK it is. The specs of 'phone lines rarely change, and there are plenty
> of 706's and 746's still in use. Maybe even the odd 300-series.
I still use a tone-dial 746 as one of my phones and a rotary dial
300-series wall mount version (don't know the number) as my other. The
only two reasons I don't use my type 332 are 1) the induction coil is
dead and 2) I have now borrowed microphone and speaker diaphragm to keep
the wall mount one going.
> Note for US types. UK 'phone wiring then was even stranger than it is
Another note for US types. Type 330 and its derivatives = pre-war
design of phone. My 332 actually has cloth insulation on internal
wires, although the (much rarer) wall mounted one has plastic
insulation. Late 1950s (?), much lighter design, PCB based, introduced,
called 706. As components got smaller, the number and size of PCBs
reduced, and the 746 has all the components, including the line drop
compensator (resistors, diodes, light bulbs) on a single PCB. This
design remained in use for around 20 years - PCB from phone circa 1970
interchangeable with PCB from phone circa 1990, the main difference
being the size of the capacitors and (if you're lucky) the provision of
a few extra screw terminals. (dial, bell, handset etc. all terminated
with ring or fork (spade) terminals to screw onto these).
I keep several type 746 phones in stock - people still occasionally want
rotary dial phones...
>> the 1960s (? What date is the 706 anyway ?), many UK phones had the
>> "line drop compensator" on a plug-in module, presumably so you could
>> swap it for one with different resistors...
>
> AFAIK the 'line drop compensator' had a constant-current barretter lamp
> on it, and there was only one version. Certainly I've only ever seen one
> version, and that's the one shown in all schematics. Alas my copy of
I've only ever seen one version, but then again, I've never seen a
schematic that actually gives the resistor values.
> You could plug the 'line drop compensator in upside-down, whereupon it
> was out of circuit and it bridged the appropriate terminals to use the
> 'phone without it. I beleive you did this at the end of very long lines.
Could be what I was thinking of.
Philip.
Hi All,
At 12:57 AM 7/17/98 +0100, you wrote:
>>
>>
>> Has anyone built any of these? Does anyone have any extra copies?
>> >Indeed it is. 1966 IIRC
>
>One day I might have a go at said robotic dog - assuming I can find
>enough DF92s, etc. Doing it in transistors wouldn't be the same :-)
>
>-tony
>
Any kind of description would be appreciated! What did it do? How many
tubes/valves, etc.?
I looked up the U.S. equivalent tube for the DF92 valve and found the
1L4. A similar one, much more common is a 1U4, used in many portable radios
before transistors. All battery filament (1.4 volts, 50mA) miniature pentodes.
>86-DOS (the base of MS-DOS 1.0) at least was developed on
a DEC 2020 station and transfered via serial line to an
INTEL ISIS system for writing Disks, or to the SCP 8086
S100 system for runntime tests.
This seems to be another one of those cases where what was once a common
software development technique is being lost to changing times. In the
70's, when micros first came out, it was common practice to buy a
cross-assembler and simulator that ran on a mini or mainframe. Code was
developed and maintained in a familiar environment, run through the
simulator, testing as much as possible, then burned into EPROM and
installed in the target system. IIRC the original IBM PC BIOS was built
this way.
When Intel came out with the 8086, they did offer an assembly language
translator for 8080 to 8086 code. For the most part there is a 1:1
correspondence for 8080 instructions, except when it came to status
flags, so the translator was relatively easy if you had a clean design.
In practical terms it was less useful because all you got was the same
program without taking advantage of the features unique to the 8086,
like segments or 16-bit operations.
Cross-assemblers were not unique to micros either. The lab where I
worked in the 70's had several stripped down DG Nova 1200s used as
embedded controllers. These machines had no console or disk, no
operating system, just a paper tape reader bootstrap and a front panel
plus some custom electronics. The development cycle was to write a
program on the mainframe (CDC 6600), punch a paper tape (yes the CDC did
have paper tape output!), load it into the Nova, sacrifice a candy bar
to the computer gods, then hit the Run switch. Debugging was front
panel lights/switches, several cases of Coke, vending machine candy, and
the good ole Single-Step toggle.
Jack Peacock
On Jul 16, 19:28, Tony Duell wrote:
> > devices play merry hell with Acorn's Tube code, which tends to see that
> > something is there but can't deal with it.
>
> :-(. What do you do on a machine with a DNFS ROM, then if you add a Torch
> Copro?
It depends on the version of the Torch ROM. In some cases, changing the
order of the MCP (for Torch Z80) and DNFS ROMs makes it usable. Usually I
softload the MCP ROM, though, else it complains if the Torch Z80 isn't
there.
> > I suspect it used the same ROM as the Z80. A colleague used to have a
> > Graduate, so I'll ask him today.
>
> Please do. I've got the Z-80 host ROM (and know of a few more if this one
is
> dead), but I don't have any other Torch ROMs.
I forgot :-( I'll remember today, honest. I've got several versions of
the MCP ROM, if you need one.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Ok, so given that there are people out there who know about phone
systems, how would I build a device that sat on the phone line and could
detect whether the line was in use or not - it's extremely annoying when
you have a modem and voice phone on the same line and your voice call
gets interrupted by a burst of modem noise! :)
btw, this is for a UK system - I've seen curcuits to do exactly this
job, but they never say whose phone systems their designed for, and I'd
imagine that US and UK systems work with different setups....
cheers
Jules
(ok, so it's not on-topic - thought I'd ask though before this thread
disappears :)
> TRS80 model II with 3 physically huge 8 meg HDDs
8 meg ? not five ? Whats the type and manufacturer ?
Do you have an online picture ?
> Phillips Micom 2000 dedicated WP with an 8" Shugart
> and a Qume daisy wheel printer that has a power supply big enough
> to power a small villiage.
Same here: Any picture for the Micom 2000 available ?
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
