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An Xmyth stack overflow ?

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  An Xmyth stack overflow ? gareth evans <headstone255@yahoo.com> - 2020-12-07 11:38 +0000
    Re: An Xmyth stack overflow ? gareth evans <headstone255@yahoo.com> - 2020-12-07 11:41 +0000
      Re: An Xmyth stack overflow ? maus <maus@dmaus.org> - 2020-12-08 15:08 +0000
        Re: An Xmyth stack overflow ? maus <maus@dmaus.org> - 2020-12-10 17:52 +0000
          Re: An Xmyth stack overflow ? Dave Garland <dave.garland@wizinfo.com> - 2020-12-10 22:46 -0600
            Re: An Xmyth stack overflow ? Mike Spencer <mds@bogus.nodomain.nowhere> - 2020-12-11 01:47 -0400
              Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-11 06:54 +0000
                Re: An Xmyth stack overflow ? Bob Eager <news0073@eager.cx> - 2020-12-11 09:46 +0000
              Re: An Xmyth stack overflow ? John Levine <johnl@taugh.com> - 2020-12-11 18:13 +0000
                Re: An Xmyth stack overflow ? Gerard Schildberger <gerard46@rrt.net> - 2020-12-11 11:29 -0800
                  Re: An Xmyth stack overflow ? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2020-12-12 01:37 +0000
                    Re: IBM 1620 and its successors, not An Xmyth stack overflow ? John Levine <johnl@taugh.com> - 2020-12-12 02:22 +0000
                      Re: IBM 1620 and its successors, not An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 06:58 -0700
                        Re: 360/44, was IBM 1620 and its successors, not An Xmyth stack overflow ? John Levine <johnl@taugh.com> - 2020-12-12 19:16 +0000
                          Re: 360/44, was IBM 1620 and its successors, not An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 19:57 -0700
                    Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-11 21:44 -0500
                    Re: An Xmyth stack overflow ? Dave Garland <dave.garland@wizinfo.com> - 2020-12-11 23:11 -0600
                      Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 06:58 -0700
                        Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 09:43 -0500
                          Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 10:31 -0500
                            Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-12 17:40 +0000
                              Re: An Xmyth stack overflow ? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2020-12-12 19:28 +0000
                            Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 13:12 -0500
                              Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 13:28 -0500
                                Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 17:35 -0500
                                  Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 17:49 -0500
                                    Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 19:31 -0500
                                      Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 19:54 -0500
                                        Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 20:08 -0500
                                          Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 19:58 -0700
                                            Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 22:13 -0500
                                          Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 23:07 -0500
                                            Re: An Xmyth stack overflow ? Dan Espen <dan1espen@gmail.com> - 2020-12-12 23:28 -0500
                                            Re: An Xmyth stack overflow ? maus <maus@dmaus.org> - 2020-12-14 19:13 +0000
                                        Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-12 23:04 -0500
                                      Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 19:57 -0700
                                        Re: An Xmyth stack overflow ? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2020-12-13 16:23 +0000
                                          Re: An Xmyth stack overflow ? J. Clarke <jclarke.873638@gmail.com> - 2020-12-13 11:47 -0500
                                          Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-13 19:18 +0000
                                            Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-13 15:11 -0700
                                              Re: An Xmyth stack overflow ? cb@elaine.df.lth.se (Christian Brunschen) - 2020-12-13 23:28 +0000
                                              Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-13 23:23 +0000
                            Re: An Xmyth stack overflow ? Niklas Karlsson <anksil@yahoo.se> - 2020-12-13 09:05 +0000
                          Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-12 19:57 -0700
                            Re: An Xmyth stack overflow ? Dave Garland <dave.garland@wizinfo.com> - 2020-12-13 11:22 -0600
                    Re: An Xmyth stack overflow ? Mike Spencer <mds@bogus.nodomain.nowhere> - 2020-12-12 01:55 -0400
            Re: An Xmyth stack overflow ? gareth evans <headstone255@yahoo.com> - 2020-12-11 11:46 +0000
              Re: An Xmyth stack overflow ? Peter Flass <peter_flass@yahoo.com> - 2020-12-11 17:22 -0700
                Re: An Xmyth stack overflow ? John Levine <johnl@taugh.com> - 2020-12-12 02:24 +0000
                Re: An Xmyth stack overflow ? Bob Eager <news0073@eager.cx> - 2020-12-12 10:16 +0000
        Re: An Xmyth stack overflow ? Mike Spencer <mds@bogus.nodomain.nowhere> - 2020-12-10 16:28 -0400
    Re: An Xmyth stack overflow ? usenet@only.tnx (Questor) - 2020-12-08 18:08 +0000
      Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-08 18:53 +0000
        Re: An Xmyth stack overflow ? gareth evans <headstone255@yahoo.com> - 2020-12-08 21:01 +0000
          Re: An Xmyth stack overflow ? Ahem A Rivet's Shot <steveo@eircom.net> - 2020-12-08 22:28 +0000
            Re: An Xmyth stack overflow ? Charlie Gibbs <cgibbs@kltpzyxm.invalid> - 2020-12-09 01:12 +0000
              Re: An Xmyth stack overflow ? gareth evans <headstone255@yahoo.com> - 2020-12-09 11:43 +0000
          Re: An Xmyth stack overflow ? drb@ihatespam.msu.edu (Dennis Boone) - 2020-12-08 20:57 -0600

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#215486

In article <2142921987.629590094.422579.peter_flass-yahoo.com@news.eternal-september.org>,
Peter Flass  <peter_flass@yahoo.com> wrote:
>Ahem A Rivet's Shot <steveo@eircom.net> wrote:
>>
>> [ ... ]  I had the CP/M port of MDBS-III
>> running in one TPA with a tiny application that just pulled parameters from
>> the shared space and put results back up there while the real application
>> ran in another TPA.

[...]

>TPA??

In CP/M, at least, the 'TPA' was the 'Transient Program Area',
see https://en.wikipedia.org/wiki/CP/M#Transient_Program_Area - essentially
the actual working RAM available to running software,  the address
space that was not in use by CP/M or the hardware in some fashion.

>-- 
>Pete

// Christian

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#215487

On Sun, 13 Dec 2020 15:11:16 -0700
Peter Flass <peter_flass@yahoo.com> wrote:

> TPA??

	Transient Program Area.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#215479

On 2020-12-12, Dan Espen <dan1espen@gmail.com> wrote:
> I remember the first PC displays were pretty poor resolution wise.
> If you wanted to really see things you went with the monochrome
> Hercules.  (Never saw one of those.)

My father's business did CAD in Hercules for a while. I remember it as
quite nice for the time.

Niklas
-- 
[It] contains "vegetable stabilizer" which sounds ominous. How unstable are vegetables? 
                       -- Jeff Zahn

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#215470

J. Clarke <jclarke.873638@gmail.com> wrote:
> On Sat, 12 Dec 2020 06:58:19 -0700, Peter Flass
> <peter_flass@yahoo.com> wrote:
> 
>> Dave Garland <dave.garland@wizinfo.com> wrote:
>>> On 12/11/2020 7:37 PM, Charlie Gibbs wrote:
>>>> On 2020-12-11, Gerard Schildberger <gerard46@rrt.net> wrote:
>>>> 
>>>>> On Friday, December 11, 2020 at 12:13:39 PM UTC-6, John Levine wrote:
>>>>> 
>>>>>> Mike Spencer  wrote:
>>>>>> 
>>>>>>> I think my Osborne I was more powerful than the IBM 1620. (Serious
>>>>>>> tecnology wonks may correct me.)
>>>>>> 
>>>>>> No doubt. The IBM 1620 was known as CADET for Can't Add, Doesn't Even
>>>>>> Try. It was a decimal serial machine and did all arithmetic by table
>>>>>> lookup. Each instruction took 100us or more. Nonetheless, it was
>>>>>> reliable and fast enough that it was used as part of the IBM 1710
>>>>>> which was the first real time process control system.
>>>>> 
>>>>> The above reply applies to the  IBM 1620 Model I  (one).
>>>>> The word  "CADET"  was the code name before the first delivery,  it was
>>>>> just a code word;  almost all IBM hardware had a code name assigned to it
>>>>> during design/production before the first delivery.   They were just names.
>>>>> The  model II  (two)  didn't use lookup tables except for multiplication.
>>>>> Model III was about to go into production,  but was cancelled because of
>>>>> the upcoming IBM 360,  and IBM didn't want anything to compete with the
>>>>> 360,  even other IBM computers.
>>>> 
>>>> Sounds familiar, like the way the original IBM Personal Computer
>>>> was crippled so as not to compete with the Displaywriter.
>>>> 
>>> It's a different market. While you could get CP/M-86 and UCSD p-System 
>>> for the D'wr (pre-IBM PC), I think it had a 1MHz CPU and CP/M-86 at 
>>> least was very sluggish compared to a 4MHz Osborne O-1. But our D'wrs 
>>> had more RAM and could run a bigger SuperCalc spreadsheet 
>>> (sluggishly).  When we did that, the challenge was making the printer 
>>> work. IBM did its classic routine, being unfailingly polite and 
>>> switching me from one person who couldn't tell me what the control 
>>> codes were to another until I gave up and did it by trial and error.
>>> 
>>> IBM later sold "Displaywrite" softwere for the PC that emulated a lot 
>>> of the software features.
>>> 
>> 
>> The display on the Displaywriter was high-quality. Going from a real
>> Displaywriter to Displaywrite on a PC was a big step backwards for anyone
>> who did a lot of word processing.
> 
> What was "high quality" about the monitor?  I did hear a lot of
> kvetching about the PC display back then but generally the people
> kvetching got the color display instead of the green screen.
> 

Hard to recall, but I think the resolution was a lot better. Of course, it
was text-only, but I seem to recall you couldn’t see the pixels in the
characters.

-- 
Pete

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#215483

On 12/12/2020 8:57 PM, Peter Flass wrote:
> J. Clarke <jclarke.873638@gmail.com> wrote:
>> On Sat, 12 Dec 2020 06:58:19 -0700, Peter Flass
>> <peter_flass@yahoo.com> wrote:
>>
>>> Dave Garland <dave.garland@wizinfo.com> wrote:
>>>> On 12/11/2020 7:37 PM, Charlie Gibbs wrote:
>>>>> On 2020-12-11, Gerard Schildberger <gerard46@rrt.net> wrote:
>>>>>
>>>>>> On Friday, December 11, 2020 at 12:13:39 PM UTC-6, John Levine wrote:
>>>>>>
>>>>>>> Mike Spencer  wrote:
>>>>>>>
>>>>>>>> I think my Osborne I was more powerful than the IBM 1620. (Serious
>>>>>>>> tecnology wonks may correct me.)
>>>>>>>
>>>>>>> No doubt. The IBM 1620 was known as CADET for Can't Add, Doesn't Even
>>>>>>> Try. It was a decimal serial machine and did all arithmetic by table
>>>>>>> lookup. Each instruction took 100us or more. Nonetheless, it was
>>>>>>> reliable and fast enough that it was used as part of the IBM 1710
>>>>>>> which was the first real time process control system.
>>>>>>
>>>>>> The above reply applies to the  IBM 1620 Model I  (one).
>>>>>> The word  "CADET"  was the code name before the first delivery,  it was
>>>>>> just a code word;  almost all IBM hardware had a code name assigned to it
>>>>>> during design/production before the first delivery.   They were just names.
>>>>>> The  model II  (two)  didn't use lookup tables except for multiplication.
>>>>>> Model III was about to go into production,  but was cancelled because of
>>>>>> the upcoming IBM 360,  and IBM didn't want anything to compete with the
>>>>>> 360,  even other IBM computers.
>>>>>
>>>>> Sounds familiar, like the way the original IBM Personal Computer
>>>>> was crippled so as not to compete with the Displaywriter.
>>>>>
>>>> It's a different market. While you could get CP/M-86 and UCSD p-System
>>>> for the D'wr (pre-IBM PC), I think it had a 1MHz CPU and CP/M-86 at
>>>> least was very sluggish compared to a 4MHz Osborne O-1. But our D'wrs
>>>> had more RAM and could run a bigger SuperCalc spreadsheet
>>>> (sluggishly).  When we did that, the challenge was making the printer
>>>> work. IBM did its classic routine, being unfailingly polite and
>>>> switching me from one person who couldn't tell me what the control
>>>> codes were to another until I gave up and did it by trial and error.
>>>>
>>>> IBM later sold "Displaywrite" softwere for the PC that emulated a lot
>>>> of the software features.
>>>>
>>>
>>> The display on the Displaywriter was high-quality. Going from a real
>>> Displaywriter to Displaywrite on a PC was a big step backwards for anyone
>>> who did a lot of word processing.
>>
>> What was "high quality" about the monitor?  I did hear a lot of
>> kvetching about the PC display back then but generally the people
>> kvetching got the color display instead of the green screen.
>>
> 
> Hard to recall, but I think the resolution was a lot better. Of course, it
> was text-only, but I seem to recall you couldn’t see the pixels in the
> characters.
> 
Correct. The D'wr monitor was text-only and not very big, but razor 
sharp. Text included some symbols and special characters for major 
Roman-alphabet languages (accents etc.). (You could configure the 
keyboard for the languages, and it had a caps-lock key that worked 
just like a typewriter and stayed down when engaged.) PCs with CGA 
weren't much use to a good typist, between the lag and the eyestrain. 
Hercules was pretty good.

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#215453

Charlie Gibbs <cgibbs@kltpzyxm.invalid> writes:

> On 2020-12-11, Gerard Schildberger <gerard46@rrt.net> wrote:
> 
>> The above reply applies to the IBM 1620 Model I (one).  The word
>> "CADET" was the code name before the first delivery, it was just a
>> code word; almost all IBM hardware had a code name assigned to it
>> during design/production before the first delivery.  They were just
>> names.  The model II (two) didn't use lookup tables except for
>> multiplication.
>> [snip]
> 
> Sounds familiar, like the way the original IBM Personal Computer
> was crippled so as not to compete with the Displaywriter.
> 
> I do love the cleverness of that CADET back-formation, though...

Digressing to arbitrary code names, I've always thought that, having
released a system called XP, Microsoft's next system might reasonably
have been expected to be called JHVH.

       Voice:  Where do you want to go today?
       Choir:  Confutatis maledictis, flammis acribus addictis

                                    -- from Mozart's Requiem
                                    -- Microsoft TV ad

-- 
Mike Spencer                  Nova Scotia, Canada

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#215442

On 11/12/2020 04:46, Dave Garland wrote:
>
> Oh hell, my 4 year old Android phone is a more powerful computer than
> the mainframe (an IBM1620) that my college had. Though the blinkenlights
> are much inferior.

Went up to Essex Uni in 1969 and their mainframe
was in the ICL1900 series.

When I left in 1972 it was a PDP10.

I wonder what they have now, nearly 50 years on?

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#215447

gareth evans <headstone255@yahoo.com> wrote:
> On 11/12/2020 04:46, Dave Garland wrote:
>> 
>> Oh hell, my 4 year old Android phone is a more powerful computer than
>> the mainframe (an IBM1620) that my college had. Though the blinkenlights
>> are much inferior.
> 
> Went up to Essex Uni in 1969 and their mainframe
> was in the ICL1900 series.
> 
> When I left in 1972 it was a PDP10.
> 
> I wonder what they have now, nearly 50 years on?
> 
> 

Probably don’t have a mainframe, but if they did it wouldn’t be as nice a 
machine as the PDP-10.

-- 
Pete

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#215450

In article <1515267408.629425216.962528.peter_flass-yahoo.com@news.eternal-september.org> you write:
>gareth evans <headstone255@yahoo.com> wrote:
>> On 11/12/2020 04:46, Dave Garland wrote:
>>> 
>>> Oh hell, my 4 year old Android phone is a more powerful computer than
>>> the mainframe (an IBM1620) that my college had. Though the blinkenlights
>>> are much inferior.
>> 
>> Went up to Essex Uni in 1969 and their mainframe
>> was in the ICL1900 series.
>> 
>> When I left in 1972 it was a PDP10.
>> 
>> I wonder what they have now, nearly 50 years on?

A bunch of Windows and Linux boxes, like everyone else:

https://www.essex.ac.uk/departments/computer-science-and-electronic-engineering/facilities

-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

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#215454

On Fri, 11 Dec 2020 17:22:10 -0700, Peter Flass wrote:

> gareth evans <headstone255@yahoo.com> wrote:
>> On 11/12/2020 04:46, Dave Garland wrote:
>>> 
>>> Oh hell, my 4 year old Android phone is a more powerful computer than
>>> the mainframe (an IBM1620) that my college had. Though the
>>> blinkenlights are much inferior.
>> 
>> Went up to Essex Uni in 1969 and their mainframe was in the ICL1900
>> series.
>> 
>> When I left in 1972 it was a PDP10.
>> 
>> I wonder what they have now, nearly 50 years on?
>> 
>> 
>> 
> Probably don’t have a mainframe, but if they did it wouldn’t be as nice
> a machine as the PDP-10.

I used that machine 1973-74! I was 2600,2645.



-- 
Using UNIX since v6 (1975)...

Use the BIG mirror service in the UK:
 http://www.mirrorservice.org

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#215437

maus <maus@dmaus.org> writes:

> The Chaos group in Germany had members interested in such things,
> from illuminating the windows of large buildings to form text
> messages, down to what you mention. Their meetings are in Leipzig
> this year.


Recall the final scene in "Hackers" and the "Crash & Burn" building?

-- 
Mike Spencer                  Nova Scotia, Canada

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#215426

On Mon, 7 Dec 2020 11:38:30 +0000, gareth evans <headstone255@yahoo.com> wrote:
>For Xmyth this year, I have 4 strings of multi-coloured LEDs
>spread out over the front garden, with a total of about 1000 LEDs
>for a total outlay of about £100.
>
>Stack overflow possibly?  After one of the strings of LEDs has cycled
>through its repertoire a number of times, they all extinguish and
>stay dark, but if I cycle the power, they all return, so it isn't
>an overheating problem.

Pop open the controller, suck out the embedded code, and debug it.
Get back to us with what you find.

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#215427

On Tue, 08 Dec 2020 18:08:56 GMT
usenet@only.tnx (Questor) wrote:

> On Mon, 7 Dec 2020 11:38:30 +0000, gareth evans <headstone255@yahoo.com>
> wrote:
> >For Xmyth this year, I have 4 strings of multi-coloured LEDs
> >spread out over the front garden, with a total of about 1000 LEDs
> >for a total outlay of about £100.
> >
> >Stack overflow possibly?  After one of the strings of LEDs has cycled
> >through its repertoire a number of times, they all extinguish and
> >stay dark, but if I cycle the power, they all return, so it isn't
> >an overheating problem.
> 
> Pop open the controller,

	Replace with a RPi Zero running a PDP-11 emulator (this is a.f.c!)
and write your own.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#215428

On 08/12/2020 18:53, Ahem A Rivet's Shot wrote:
> On Tue, 08 Dec 2020 18:08:56 GMT
> usenet@only.tnx (Questor) wrote:
>
>> On Mon, 7 Dec 2020 11:38:30 +0000, gareth evans <headstone255@yahoo.com>
>> wrote:
>>> For Xmyth this year, I have 4 strings of multi-coloured LEDs
>>> spread out over the front garden, with a total of about 1000 LEDs
>>> for a total outlay of about £100.
>>>
>>> Stack overflow possibly?  After one of the strings of LEDs has cycled
>>> through its repertoire a number of times, they all extinguish and
>>> stay dark, but if I cycle the power, they all return, so it isn't
>>> an overheating problem.
>>
>> Pop open the controller,
>
> 	Replace with a RPi Zero running a PDP-11 emulator (this is a.f.c!)
> and write your own.
>

It raises a question about the integration inside the LEDs themselves,
because only two wires come out of the controller / wall wart and yet
the string sequencing drives the LEDs into two distinct groups.

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#215429

On Tue, 8 Dec 2020 21:01:07 +0000
gareth evans <headstone255@yahoo.com> wrote:

> On 08/12/2020 18:53, Ahem A Rivet's Shot wrote:
> > On Tue, 08 Dec 2020 18:08:56 GMT
> > usenet@only.tnx (Questor) wrote:
> >
> >> On Mon, 7 Dec 2020 11:38:30 +0000, gareth evans
> >> <headstone255@yahoo.com> wrote:
> >>> For Xmyth this year, I have 4 strings of multi-coloured LEDs
> >>> spread out over the front garden, with a total of about 1000 LEDs
> >>> for a total outlay of about £100.
> >>>
> >>> Stack overflow possibly?  After one of the strings of LEDs has cycled
> >>> through its repertoire a number of times, they all extinguish and
> >>> stay dark, but if I cycle the power, they all return, so it isn't
> >>> an overheating problem.
> >>
> >> Pop open the controller,
> >
> > 	Replace with a RPi Zero running a PDP-11 emulator (this is
> > a.f.c!) and write your own.
> >
> 
> It raises a question about the integration inside the LEDs themselves,
> because only two wires come out of the controller / wall wart and yet
> the string sequencing drives the LEDs into two distinct groups.

	The D in LED may be significant here, perhaps half of them are one
way round and half the other with the supply reversing polarity[1] to switch
sets.

[1] of the electron flow.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

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#215430

On 2020-12-08, Ahem A Rivet's Shot <steveo@eircom.net> wrote:

> On Tue, 8 Dec 2020 21:01:07 +0000
> gareth evans <headstone255@yahoo.com> wrote:
>
>> It raises a question about the integration inside the LEDs themselves,
>> because only two wires come out of the controller / wall wart and yet
>> the string sequencing drives the LEDs into two distinct groups.
>
> 	The D in LED may be significant here, perhaps half of them are one
> way round and half the other with the supply reversing polarity[1] to switch
> sets.
>
> [1] of the electron flow.

That was my first thought.  That reminds me of an article I once read by
a railroad modeler who found a unit that combined red and green LEDs in
a single package.  He used it to create a track signal.  Apply DC one way
and it lit up red, apply DC the other way and it lit up green - and apply
AC and it lit up yellow.  Cute.

-- 
/~\  Charlie Gibbs                  |  "Some of you may die,
\ /  <cgibbs@kltpzyxm.invalid>      |  but it's a sacrifice
 X   I'm really at ac.dekanfrus     |  I'm willing to make."
/ \  if you read it the right way.  |    -- Lord Farquaad (Shrek)

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#215432

On 09/12/2020 01:12, Charlie Gibbs wrote:
> On 2020-12-08, Ahem A Rivet's Shot <steveo@eircom.net> wrote:
>
>> On Tue, 8 Dec 2020 21:01:07 +0000
>> gareth evans <headstone255@yahoo.com> wrote:
>>
>>> It raises a question about the integration inside the LEDs themselves,
>>> because only two wires come out of the controller / wall wart and yet
>>> the string sequencing drives the LEDs into two distinct groups.
>>
>> 	The D in LED may be significant here, perhaps half of them are one
>> way round and half the other with the supply reversing polarity[1] to switch
>> sets.
>>
>> [1] of the electron flow.
>
> That was my first thought.  That reminds me of an article I once read by
> a railroad modeler who found a unit that combined red and green LEDs in
> a single package.  He used it to create a track signal.  Apply DC one way
> and it lit up red, apply DC the other way and it lit up green - and apply
> AC and it lit up yellow.  Cute.
>

Reminds me of the time (40+ years ago) working on automation in
coal mines. (The MINOS system from MRDE at Bretby).

Any remote alarm signal resulted in an open contact, with the
safe postiion being normally closed but in series with a diode,
with the excitation being AC.

This resulted in three distinct signals ...

No signal; either the alarm or the line has been cut.

Halfrectified DC;  No alarm.

Full AC; the line has been short circuited somewhere.

This arrangement was known as Line Proving.

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#215431

 > It raises a question about the integration inside the LEDs themselves,
 > because only two wires come out of the controller / wall wart and yet
 > the string sequencing drives the LEDs into two distinct groups.

Many of these strings of LEDs use a shift-in / shift-out model where you
clock out settings for each LED in turn.  The LEDs are in series on the
line, and when new data arrives, they shift the previous data on down
the line, and at the end of sending enough for each LED, the first
setting out has reached the end of the string.

De

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