Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Tuesday 17 December 2019 12:44:47 Dave Matthews wrote:

> On Tue, Dec 17, 2019 at 9:22 AM Peter C. Wallace  
wrote:
> > You can get really bad base jitter if you try to run the base thread
> > faster than the machine is capable of responding (the latency-tests
> > default 40 KHz base thread is too fast for some systems so you might
> > get considerably better reported latency at 20 KHz for example)
> >
> >
> > Peter Wallace
> > Mesa Electronics
>
> For those of us in the cheap seats how does the base thread frequency
> relate to the maximum number of words per second sent to the parallel
> port?  I figure 20k words / second would work out to 375 inches /
> minute of travel on my homebuilt CNC router.  Far faster than I would
> need and thus in the range of not needing to worry about it all that
> much.
>
> Dave
>
There is also the effect of variable latency to concider, and its very 
very important with software stepping.  Imagine when moving that near 
your calculated speed limit, and something disturbs the timeing of the 
steps.

The motor effectively stops, then the high speed signals resume.  But 
they resume at the current speed without the acceleration rampup in 
speed that accompany's the speed change.

Unless you have motors are wound on air cores, and the copper in the 
windings is also zero weight, a massless rotor in effect, the motor is 
not capable of resumeing that speed so it locks in place until the step 
rate received is low enough to allow it to restart.  But because it will 
restart at any of it 200 positions, lcnc has lost the reference point to 
the axis only and your part is wrecked. 

This is your REAL speed limit, and because the table has varying drag, 
increaseing as your approach ends of travel, your need additional head 
room.

The end result can often be 10% or less of what your calculations show.

Generally speaking that is still faster than the spindle horsepower 
provides for, and as those limits apply only to the rapid moves, and 
will probably be cutting air.

And its a lesson that cost me some broken tools and wrecked parts to 
learn.

And since every system involving springs has a resonant frequency that is 
often well below this speed limit, the motors magnetic bounce will cause 
the stalling to manifest itself at even lower speeds, so 
torsional "dampers" will often result in much hugher speeds as they 
dampen the resonance, in one case here a 435 oz motor as the vertical 
(Z) motor on a baby hf mill, went from an 8 ipm speed limit, to 34 ipm. 
That axis was not a ball screw, but a double nutted NOOK acme that I 
could adjust for about .0005" of backlash in a rotating nut design. You 
can see pix of these dampers on my web page. Those are alternating big 
steel fender washers with powdered (talcum) rubber disks cut out of 1/8 
thick rubber but the center holes in the rubber are smaller than the 
spools hub, so the center of the washer when installed is few thou 
fatter.  So the steel to rubber slips and the slippage is the resonance 
absorber. There are of coarse other designs. Choose your poison.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Tuesday 17 December 2019 13:41:09 Dave Matthews wrote:

> On Tue, Dec 17, 2019 at 12:55 PM andy pugh  wrote:
> > On Tue, 17 Dec 2019 at 17:47, Dave Matthews  wrote:
> > > For those of us in the cheap seats how does the base thread
> > > frequency relate to the maximum number of words per second sent to
> > > the parallel port?
> >
> > The system can send a maximum of one pulse per base period.
>
> And that pulse contains the information for all of the motors being
> controlled.  Correct?
>
> Dave
>
Afaik, yes.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Tuesday 17 December 2019 13:18:10 Eric Keller wrote:

> In the past, I have had a reasonable amount of luck reducing real time
> delays by building a custom kernel.  Not sure if those kinds of gains
> are still possible.  And it's a lot of work unless you are using
> realtime preempt.
>
> As far as Gene's problem with the beep, they are probably using the
> 8051 on the system management bus for that.  I wonder if a sound card
> would have the same problem. I think most beeps can be routed through
> the sound card. Eric Keller
> Boalsburg, Pennsylvania
>
Probably could be done, but as has been said, this is my house machine, 
and newly built and will never cut metal.  I've to had no chance to fine 
tune yet, as I am just this afternoon back from a couple days in the 
shop, getting new Aortic valve in the top of my heart. It seems to be 
working well.

For those that observe Christmas, have a Merry one.
>
> On Mon, Dec 16, 2019 at 9:19 PM John Dammeyer 
>
> wrote:
> > > > For example.  The board in the machine at the moment generates a
> > > > Servo Jitter of 33217 and Base Jitter of 131983.
> > >
> > > Thats pretty slow john, I'd take that machine to the office and
> > > bring out the office machine.  It might just be faster. :)
> >
> > Yes Gene,
> > I sometimes wonder if there is something else going on.  Something
> > the BIOS settings that makes these two machines so slow.  Processor
> > and memory wise they should be more than adequate.  They weren't
> > expensive as they were used.  But what's to say if I went to COSTCO
> > and bought a new one that I'd be any better off.
> >
> > John
> >
> >
> >
> >
> > ___
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> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Latency Warning Messages

[Dave Matthews]

On Tue, Dec 17, 2019 at 2:00 PM John Dammeyer  wrote:
>
> Actually I think it's at one pulse per two base periods.  One to set the step 
> signals high, one to set them low.  The document referenced by "bari",
>
> How to choose your base period:
> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGeneration
>
> explains that in detail.
> John Dammeyer
>
Thank you, I hadn't seen that bit of documentation.  Looks like I can
do about 285 in/min with my current setup without any tweaking.  Half
of that is a realistic speed for my Gatton CNC to do rapids.

Dave


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Re: [Emc-users] Latency Warning Messages

[andy pugh]

On Tue, 17 Dec 2019 at 19:00, John Dammeyer  wrote:
>
> Actually I think it's at one pulse per two base periods.  One to set the step 
> signals high, one to set them low.

The parport driver offers a "reset" function that sets selected pins
back to zero. You can run this later in the thread than the "write"
function and it either resets the pins immediately if the step time
has expired, or waits a few µS for that to happen then resets.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Latency Warning Messages

[John Dammeyer]

Actually I think it's at one pulse per two base periods.  One to set the step 
signals high, one to set them low.  The document referenced by "bari",

How to choose your base period:
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGeneration

explains that in detail.
John Dammeyer


> -Original Message-
> From: Dave Matthews [mailto:n36...@gmail.com]
> Sent: December-17-19 10:41 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Latency Warning Messages
> 
> On Tue, Dec 17, 2019 at 12:55 PM andy pugh  wrote:
> >
> > On Tue, 17 Dec 2019 at 17:47, Dave Matthews  wrote:
> >
> > > For those of us in the cheap seats how does the base thread frequency
> > > relate to the maximum number of words per second sent to the parallel
> > > port?
> >
> > The system can send a maximum of one pulse per base period.
> >
> 
> And that pulse contains the information for all of the motors being
> controlled.  Correct?
> 
> Dave
> 
> 
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Re: [Emc-users] Latency Warning Messages

[Dave Matthews]

On Tue, Dec 17, 2019 at 12:55 PM andy pugh  wrote:
>
> On Tue, 17 Dec 2019 at 17:47, Dave Matthews  wrote:
>
> > For those of us in the cheap seats how does the base thread frequency
> > relate to the maximum number of words per second sent to the parallel
> > port?
>
> The system can send a maximum of one pulse per base period.
>

And that pulse contains the information for all of the motors being
controlled.  Correct?

Dave


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Re: [Emc-users] Latency Warning Messages

[Eric Keller]

In the past, I have had a reasonable amount of luck reducing real time
delays by building a custom kernel.  Not sure if those kinds of gains are
still possible.  And it's a lot of work unless you are using realtime
preempt.

As far as Gene's problem with the beep, they are probably using the 8051 on
the system management bus for that.  I wonder if a sound card would have
the same problem. I think most beeps can be routed through the sound card.
Eric Keller
Boalsburg, Pennsylvania



On Mon, Dec 16, 2019 at 9:19 PM John Dammeyer 
wrote:

> > >
> > > For example.  The board in the machine at the moment generates a Servo
> > > Jitter of 33217 and Base Jitter of 131983.
>
>
> > Thats pretty slow john, I'd take that machine to the office and bring out
> > the office machine.  It might just be faster. :)
> >
>
> Yes Gene,
> I sometimes wonder if there is something else going on.  Something the
> BIOS settings that makes these two machines so slow.  Processor and memory
> wise they should be more than adequate.  They weren't expensive as they
> were used.  But what's to say if I went to COSTCO and bought a new one that
> I'd be any better off.
>
> John
>
>
>
>
> ___
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>

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Re: [Emc-users] Latency Warning Messages

[andy pugh]

On Tue, 17 Dec 2019 at 17:47, Dave Matthews  wrote:

> For those of us in the cheap seats how does the base thread frequency
> relate to the maximum number of words per second sent to the parallel
> port?

The system can send a maximum of one pulse per base period.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Latency Warning Messages

[Dave Matthews]

On Tue, Dec 17, 2019 at 9:22 AM Peter C. Wallace  wrote:
>
> You can get really bad base jitter if you try to run the base thread faster 
> than
> the machine is capable of responding (the latency-tests default 40 KHz base
> thread is too fast for some systems so you might get considerably better
> reported latency at 20 KHz for example)
>
>
> Peter Wallace
> Mesa Electronics
>
For those of us in the cheap seats how does the base thread frequency
relate to the maximum number of words per second sent to the parallel
port?  I figure 20k words / second would work out to 375 inches /
minute of travel on my homebuilt CNC router.  Far faster than I would
need and thus in the range of not needing to worry about it all that
much.

Dave


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Re: [Emc-users] Latency Warning Messages

[Peter C. Wallace]

On Tue, 17 Dec 2019, andy pugh wrote:



Date: Tue, 17 Dec 2019 11:32:22 +
From: andy pugh 
Reply-To: "Enhanced Machine Controller (EMC)"

To: "Enhanced Machine Controller (EMC)" 
Subject: Re: [Emc-users] Latency Warning Messages

On Mon, 16 Dec 2019 at 23:42, John Dammeyer  wrote:

For example.  The board in the machine at the moment generates a
Servo Jitter of 33217 and Base Jitter of 131983.



That's fairly terrible.



Out of interest, how well does that machine work with Mach3?


You can get really bad base jitter if you try to run the base thread faster than 
the machine is capable of responding (the latency-tests default 40 KHz base 
thread is too fast for some systems so you might get considerably better 
reported latency at 20 KHz for example)



Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.



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Re: [Emc-users] Latency Warning Messages

[andy pugh]

On Mon, 16 Dec 2019 at 23:42, John Dammeyer  wrote:

> For example.  The board in the machine at the moment generates a Servo Jitter 
> of 33217 and Base Jitter of 131983.

That's fairly terrible.

Out of interest, how well does that machine work with Mach3?

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Monday 16 December 2019 23:12:20 bari wrote:

> On 12/16/19 9:02 PM, Gene Heskett wrote:
> > intel cpus are better than equ dated amd's, my old quad core phenom
> > was phenominally bad at latency-test. 100+ microseconds. New 9th gen
> > 6 core i5, 4 or 5 microseconds. Till kmail beeps the chassis
> > speaker, then its 200 u-secs.
>
> BIOS issues likely since Phenom and Phenom II's were used for most the
> RTAI work from '12-'14 and we had them in the low single digit
> microseconds.
>
I had the latest available on an Asus M2N-SLI Deluxe. Several of the 
linuxcnc kernels ran as daily drivers over the years since I built it in 
2006. It was stuck in the 100 microsecond region. Original phenom, only 
aavailable for a month or so when I bought it, ordered slower 2.1 GHz 
version and never really pushed as it was a room heater anyway. This 6 
core i5 runs 30C cooler than the phenom, and its doing it at 3.7GHz. 

By '12 or '14, the phenoms had been optimized enough there likely could 
be considered a new family, die shrinks etc had pulled the fastest ones 
down to 95 watts. I inquired at Asus in about that time frame and was 
told the later ones wouldn't run on that nearly $300 board.

Then that board burned up starting at one of the usb headers about 3 
weeks back so I had to rebuild it. So this time I spent more on the cpu 
and less on the board.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Latency Warning Messages

[bari]

On 12/16/19 9:02 PM, Gene Heskett wrote:
> intel cpus are better than equ dated amd's, my old quad core phenom was 
> phenominally bad at latency-test. 100+ microseconds. New 9th gen 6 core 
> i5, 4 or 5 microseconds. Till kmail beeps the chassis speaker, then its 
> 200 u-secs.
BIOS issues likely since Phenom and Phenom II's were used for most the
RTAI work from '12-'14 and we had them in the low single digit microseconds.


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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Monday 16 December 2019 21:17:40 John Dammeyer wrote:

> > > For example.  The board in the machine at the moment generates a
> > > Servo Jitter of 33217 and Base Jitter of 131983.
> >
> > Thats pretty slow john, I'd take that machine to the office and
> > bring out the office machine.  It might just be faster. :)
>
> Yes Gene,
> I sometimes wonder if there is something else going on.  Something the
> BIOS settings that makes these two machines so slow.  Processor and
> memory wise they should be more than adequate.  They weren't expensive
> as they were used.  But what's to say if I went to COSTCO and bought a
> new one that I'd be any better off.
>
> John

At costco? That would be tossing quarters, and hoping they come back down

General rules of thumb I have observed:

intel cpus are better than equ dated amd's, my old quad core phenom was 
phenominally bad at latency-test. 100+ microseconds. New 9th gen 6 core 
i5, 4 or 5 microseconds. Till kmail beeps the chassis speaker, then its 
200 u-secs.

Nvidia video cards being driven by nvidia drivers are horrible, returning 
2 or 3 milliseconds, the nouveau driver may not be as fast for video, 
but it doesn't lock out the irq's either, so its actually quite a bit 
better. But linux drivers pushing an ATI card were usually best. ATI is 
now part of AMD but haven't checked the numbers there in several years.

So far, nothing beats the intel atom powered D-525-MW mobo for good 
latency and more than enough cojones even w/o a mesa card to software 
step.  But they've been discoed for quite a few years now, so the only 
place to get them is ebay, and I'm a little shy about paying 20 to 50 
bucks more than new for used. I have mesa 5i25 cards in both of mine 
now, with 7i76D daughter cards.

However, I am pleasantly surprised at how well an rpi4b is running my 
sheldon lathe.

>
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
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Re: [Emc-users] Latency Warning Messages

[bari]

On 12/16/19 5:40 PM, John Dammeyer wrote:
>
> For example.  The board in the machine at the moment generates a Servo Jitter 
> of 33217 and Base Jitter of 131983.   
> For the MESA and PP configuration I have:
> BASE_PERIOD = 24000
> SERVO_PERIOD = 100
>
> If I understood the document link above correctly I should have set the base 
> to at least 132000 which would limit my step rate to about 3kHz.  The video 
> board is a ow profile card that has a DVI connector out and can run to two 
> VGA monitors.  Really just designed for desktop PC's that need multiple 
> monitors to display government forms or whatever.  The Lenovo PC and card 
> came from the government surplus.
>
> Now if I remove the video card and run the latency test for the on board 
> video I get a Servo Jitter of 351232 and Base Jitter of 418333.
>
> Setting the .ini BASE_PERIOD to 420,000 results in no longer getting the 
> initial servo message.  Of course now step rates are so severely restricted 
> that jog on the X axis results in an immediate following error.
>
Yes it shounds like you are understanding the docs.

Have you turned off all the power management in BIOS along with any
speed stepping any virtualization? All should off and not used.

If you have all these off then the motherboard and CPU chosen is not a
low latency combo. Often the BIOSes are broken and even though you have
them off they may not really be off.




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Re: [Emc-users] Latency Warning Messages

[John Dammeyer]

> >
> > For example.  The board in the machine at the moment generates a Servo
> > Jitter of 33217 and Base Jitter of 131983.


> Thats pretty slow john, I'd take that machine to the office and bring out
> the office machine.  It might just be faster. :)
> 

Yes Gene,
I sometimes wonder if there is something else going on.  Something the BIOS 
settings that makes these two machines so slow.  Processor and memory wise they 
should be more than adequate.  They weren't expensive as they were used.  But 
what's to say if I went to COSTCO and bought a new one that I'd be any better 
off.

John




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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Monday 16 December 2019 18:40:35 John Dammeyer wrote:

> > -Original Message-
> > From: bari [mailto:bari00...@gmail.com]
> > Sent: December-16-19 10:51 AM
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] Latency Warning Messages
> >
> > It depends on how you configure and run Linuxcnc with your intended
> > hardware.
> >
> > In the .INI file there is a section EMCMOT
> > http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:EMCMOT-
> > section
> >
> > The settings you place in BASE_PERIOD and SERVO_PERIOD set the
> > length of each of these task periods for Linuxcnc.
> >
> > BASE_PERIOD = 5 - the Base task period in nanoseconds.
> >
> > SERVO_PERIOD = 100 - This is the "Servo" task period in
> > nanoseconds.
> >
> > If either thread run by the processor takes longer than the times in
> > these settings you will see a latency message for it taking too
> > long. This can be caused by things like trying to step too quickly
> > (moving the motors faster) using the base period with a LPT port or
> > by using too low a setting for the task periods to begin with based
> > on your hardware and BIOS settings.
> >
> > How to choose your base period:
> > http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGenerat
> >ion
> >
> > The reason that you stopped having the latency messages when you
> > changed
> > from software stepping on the LPT port to hardware stepping on the
> > MESA 7i92H is that you changed from using the Base Period (very
> > short, fast) to the Servo Period (much slower) from the CPU's
> > perspective. This allows you to use a PC with longer latency or
> > higher jitter.
> >
> > On 12/16/19 12:03 PM, John Dammeyer wrote:
> > > That's what I've found.  When I run the test software to determine
> >
> > machine latency the on board video provides the smallest number. 
> > Any of the add on boards I tried all gave much worse numbers.
>
> For example.  The board in the machine at the moment generates a Servo
> Jitter of 33217 and Base Jitter of 131983.
Thats pretty slow john, I'd take that machine to the office and bring out 
the office machine.  It might just be faster. :)

> For the MESA and PP 
> configuration I have:
> BASE_PERIOD = 24000
> SERVO_PERIOD = 100
>
> If I understood the document link above correctly I should have set
> the base to at least 132000 which would limit my step rate to about
> 3kHz.  The video board is a ow profile card that has a DVI connector
> out and can run to two VGA monitors.  Really just designed for desktop
> PC's that need multiple monitors to display government forms or
> whatever.  The Lenovo PC and card came from the government surplus.
>
> Now if I remove the video card and run the latency test for the on
> board video I get a Servo Jitter of 351232 and Base Jitter of 418333.
>
> Setting the .ini BASE_PERIOD to 420,000 results in no longer getting
> the initial servo message.  Of course now step rates are so severely
> restricted that jog on the X axis results in an immediate following
> error.
>
> I believe that the DC Servos are more forgiving if the step pulses are
> occasionally held back since the internal step counter is compared
> against the encoder counter and a following error fault by the motor
> only happens if it reads more encoder counts than received on the step
> input.  Probably why with the video board installed and the initial
> error that I don't get faults.
>
> And none of that is an issue with the MESA card.
> John
>
> > > Also, if I understand how this works, if the fastest speed
> > > required for
> >
> > stepping is not to high then you won't get the messages.  But if
> > your step rates are up into 50kHz and higher then you get that
> > warning once when you start up LinuxCNC.
> >
> > > But I may have it all wrong.   For my current testing I get that
> > > message
> >
> > when I use the parallel port but it doesn't appear to affect the
> > step rates to the drives.  I just dispose of the message.  But
> > that's because I don't care at the moment.  I'll switch to the MESA
> > once the testing and development is done.
> >
> > > John
> > >
> > >> -Original Message-
> > >> From: N [mailto:nicklas.karlsso...@gmail.com]
> > >> Sent: December-16-19 9:38 AM
> > >> To: Enhanced Machine Controller (EMC)
> > >> Subject: Re: [Emc-users] Latency Warning Messages
> > >>
> > >>> I bought 3 different low p

Re: [Emc-users] Latency Warning Messages

[John Dammeyer]

> -Original Message-
> From: bari [mailto:bari00...@gmail.com]
> Sent: December-16-19 10:51 AM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Latency Warning Messages
> 
> It depends on how you configure and run Linuxcnc with your intended
> hardware.
> 
> In the .INI file there is a section EMCMOT
> http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:EMCMOT-
> section
> 
> The settings you place in BASE_PERIOD and SERVO_PERIOD set the length of
> each of these task periods for Linuxcnc.
> 
> BASE_PERIOD = 5 - the Base task period in nanoseconds.
> 
> SERVO_PERIOD = 100 - This is the "Servo" task period in nanoseconds.
> 
> If either thread run by the processor takes longer than the times in
> these settings you will see a latency message for it taking too long.
> This can be caused by things like trying to step too quickly (moving the
> motors faster) using the base period with a LPT port or by using too low
> a setting for the task periods to begin with based on your hardware and
> BIOS settings.
> 
> How to choose your base period:
> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGeneration
> 
> The reason that you stopped having the latency messages when you
> changed
> from software stepping on the LPT port to hardware stepping on the MESA
> 7i92H is that you changed from using the Base Period (very short, fast)
> to the Servo Period (much slower) from the CPU's perspective. This
> allows you to use a PC with longer latency or higher jitter.
> 
> On 12/16/19 12:03 PM, John Dammeyer wrote:
> > That's what I've found.  When I run the test software to determine
> machine latency the on board video provides the smallest number.  Any of
> the add on boards I tried all gave much worse numbers.

For example.  The board in the machine at the moment generates a Servo Jitter 
of 33217 and Base Jitter of 131983.   
For the MESA and PP configuration I have:
BASE_PERIOD = 24000
SERVO_PERIOD = 100

If I understood the document link above correctly I should have set the base to 
at least 132000 which would limit my step rate to about 3kHz.  The video board 
is a ow profile card that has a DVI connector out and can run to two VGA 
monitors.  Really just designed for desktop PC's that need multiple monitors to 
display government forms or whatever.  The Lenovo PC and card came from the 
government surplus.

Now if I remove the video card and run the latency test for the on board video 
I get a Servo Jitter of 351232 and Base Jitter of 418333.

Setting the .ini BASE_PERIOD to 420,000 results in no longer getting the 
initial servo message.  Of course now step rates are so severely restricted 
that jog on the X axis results in an immediate following error.

I believe that the DC Servos are more forgiving if the step pulses are 
occasionally held back since the internal step counter is compared against the 
encoder counter and a following error fault by the motor only happens if it 
reads more encoder counts than received on the step input.  Probably why with 
the video board installed and the initial error that I don't get faults.

And none of that is an issue with the MESA card.
John



> >
> > Also, if I understand how this works, if the fastest speed required for
> stepping is not to high then you won't get the messages.  But if your step
> rates are up into 50kHz and higher then you get that warning once when you
> start up LinuxCNC.
> >
> > But I may have it all wrong.   For my current testing I get that message
> when I use the parallel port but it doesn't appear to affect the step rates to
> the drives.  I just dispose of the message.  But that's because I don't care 
> at
> the moment.  I'll switch to the MESA once the testing and development is
> done.
> >
> > John
> >
> >> -Original Message-
> >> From: N [mailto:nicklas.karlsso...@gmail.com]
> >> Sent: December-16-19 9:38 AM
> >> To: Enhanced Machine Controller (EMC)
> >> Subject: Re: [Emc-users] Latency Warning Messages
> >>
> >>> I bought 3 different low profile video cards to try and get rid of that
> latency
> >> message.  The ultimate and best solution was to buy the MESA 7i92H.
> Does
> >> away with the parallel port completely.
> >>> John Dammeyer
> >> The parrallel port cause latency messages?
> >>
> >>
> >> ___
> >> Emc-users mailing list
> >> Emc-users@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourcef

Re: [Emc-users] Latency Warning Messages

[bari]

It depends on how you configure and run Linuxcnc with your intended
hardware.

In the .INI file there is a section EMCMOT
http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:EMCMOT-section

The settings you place in BASE_PERIOD and SERVO_PERIOD set the length of
each of these task periods for Linuxcnc.

BASE_PERIOD = 5 - the Base task period in nanoseconds.

SERVO_PERIOD = 100 - This is the "Servo" task period in nanoseconds.

If either thread run by the processor takes longer than the times in
these settings you will see a latency message for it taking too long.
This can be caused by things like trying to step too quickly (moving the
motors faster) using the base period with a LPT port or by using too low
a setting for the task periods to begin with based on your hardware and
BIOS settings.

How to choose your base period:
http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGeneration

The reason that you stopped having the latency messages when you changed
from software stepping on the LPT port to hardware stepping on the MESA
7i92H is that you changed from using the Base Period (very short, fast)
to the Servo Period (much slower) from the CPU's perspective. This
allows you to use a PC with longer latency or higher jitter.

On 12/16/19 12:03 PM, John Dammeyer wrote:
> That's what I've found.  When I run the test software to determine machine 
> latency the on board video provides the smallest number.  Any of the add on 
> boards I tried all gave much worse numbers.
>
> Also, if I understand how this works, if the fastest speed required for 
> stepping is not to high then you won't get the messages.  But if your step 
> rates are up into 50kHz and higher then you get that warning once when you 
> start up LinuxCNC.
>
> But I may have it all wrong.   For my current testing I get that message when 
> I use the parallel port but it doesn't appear to affect the step rates to the 
> drives.  I just dispose of the message.  But that's because I don't care at 
> the moment.  I'll switch to the MESA once the testing and development is done.
>
> John
>
>> -Original Message-
>> From: N [mailto:nicklas.karlsso...@gmail.com]
>> Sent: December-16-19 9:38 AM
>> To: Enhanced Machine Controller (EMC)
>> Subject: Re: [Emc-users] Latency Warning Messages
>>
>>> I bought 3 different low profile video cards to try and get rid of that 
>>> latency
>> message.  The ultimate and best solution was to buy the MESA 7i92H.  Does
>> away with the parallel port completely.
>>> John Dammeyer
>> The parrallel port cause latency messages?
>>
>>
>> ___
>> Emc-users mailing list
>> Emc-users@lists.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
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Re: [Emc-users] Latency Warning Messages

[Gene Heskett]

On Monday 16 December 2019 12:38:18 N wrote:

> > I bought 3 different low profile video cards to try and get rid of
> > that latency message.  The ultimate and best solution was to buy the
> > MESA 7i92H.  Does away with the parallel port completely. John
> > Dammeyer
>
> The parrallel port cause latency messages?
>
Some motherboards route an "out" thru a lot of junk to get there.
>
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Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] Latency Warning Messages

[John Dammeyer]

That's what I've found.  When I run the test software to determine machine 
latency the on board video provides the smallest number.  Any of the add on 
boards I tried all gave much worse numbers.

Also, if I understand how this works, if the fastest speed required for 
stepping is not to high then you won't get the messages.  But if your step 
rates are up into 50kHz and higher then you get that warning once when you 
start up LinuxCNC.

But I may have it all wrong.   For my current testing I get that message when I 
use the parallel port but it doesn't appear to affect the step rates to the 
drives.  I just dispose of the message.  But that's because I don't care at the 
moment.  I'll switch to the MESA once the testing and development is done.

John

> -Original Message-
> From: N [mailto:nicklas.karlsso...@gmail.com]
> Sent: December-16-19 9:38 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] Latency Warning Messages
> 
> > I bought 3 different low profile video cards to try and get rid of that 
> > latency
> message.  The ultimate and best solution was to buy the MESA 7i92H.  Does
> away with the parallel port completely.
> > John Dammeyer
> 
> The parrallel port cause latency messages?
> 
> 
> ___
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> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users



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Re: [Emc-users] Latency Warning Messages

[N]

> I bought 3 different low profile video cards to try and get rid of that 
> latency message.  The ultimate and best solution was to buy the MESA 7i92H.  
> Does away with the parallel port completely.
> John Dammeyer

The parrallel port cause latency messages?


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Re: [Emc-users] Latency Warning Messages

[andy pugh]

On Mon, 16 Dec 2019 at 05:47, Thomas D. Dean  wrote:

> Looks like the on-board video adapter shares main memory with the CPU.
> Linuxcnc system requirements says this is a no=no.

That advice might be outdated, I have many systems that seem perfectly
happy with this.

> Question:  Will installing a PCI video card likely to reduce the latency
> and eliminate the warnings?

It might, but there are probably other solutions.

If the "Stretch" drive can be considered disposable, you could try
installing a 64-bit Debian Buster on there, and then try out the
experimental 64-bit RTAI packages in http://www.linuxcnc.org/temp/

(This assumes that your PC can run 64-bit linux. Some D2500 can't
(depending on motherboard) but it sounds like 64-bit stretch is
working)

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Latency Warning Messages

[John Dammeyer]

I bought 3 different low profile video cards to try and get rid of that latency 
message.  The ultimate and best solution was to buy the MESA 7i92H.  Does away 
with the parallel port completely.
John Dammeyer


> -Original Message-
> From: Thomas D. Dean [mailto:tomd...@wavecable.com]
> Sent: December-15-19 9:46 PM
> To: 'Enhanced Machine Controller (EMC)'
> Subject: [Emc-users] Latency Warning Messages
> 
> My CNC computer was purchased several years ago from Sherline with CNC
> installed.
> 
> I have two disk drives.  One has linuxcnc-2.7.14-wheezy.iso and the
> other has linuxcnc-stretch-uspace-amd64.iso.
> 
> On both OS's, I see 'unexpected latency warning messages', infrequent on
> 'wheezy' and 99% of the time at linuxcnc startup on 'stretch'.  The
> latency test shows jitter around 40us for 'wheezy' and 100us for 'stretch'.
> 
> The cpu is Intel Atom CPU D2500   @ 1.86GHz
> It has 1G memory.
> Lots of free disk space.
> 
> lspci shows:
> 00:02.0 VGA compatible controller: Intel Corporation Atom Processor
> D2xxx/N2xxx Integrated Graphics Controller (rev 0b)
> 
> and lspci -v shows:
> 00:02.0 VGA compatible controller: Intel Corporation Atom Processor
> D2xxx/N2xxx Integrated Graphics Controller (rev 0b) (prog-if 00 [VGA
> controller])
>  Subsystem: Intel Corporation Atom Processor D2xxx/N2xxx
> Integrated Graphics Controller
>  Flags: bus master, fast devsel, latency 0, IRQ 29
>  Memory at 4010 (32-bit, non-prefetchable) [size=1M]
>  I/O ports at 20d0 [size=8]
>  [virtual] Expansion ROM at 000c [disabled] [size=128K]
>  Capabilities: [d0] Power Management version 2
>  Capabilities: [b0] Vendor Specific Information: Len=07 
>  Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
>  Kernel driver in use: gma500
>  Kernel modules: gma500_gfx
> 
> Looks like the on-board video adapter shares main memory with the CPU.
> Linuxcnc system requirements says this is a no=no.
> 
> Question:  Will installing a PCI video card likely to reduce the latency
> and eliminate the warnings?
> 
> Tom Dean
> 
> 
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[Emc-users] Latency Warning Messages

[Thomas D. Dean]

My CNC computer was purchased several years ago from Sherline with CNC 
installed.


I have two disk drives.  One has linuxcnc-2.7.14-wheezy.iso and the 
other has linuxcnc-stretch-uspace-amd64.iso.


On both OS's, I see 'unexpected latency warning messages', infrequent on 
'wheezy' and 99% of the time at linuxcnc startup on 'stretch'.  The 
latency test shows jitter around 40us for 'wheezy' and 100us for 'stretch'.


The cpu is Intel Atom CPU D2500   @ 1.86GHz
It has 1G memory.
Lots of free disk space.

lspci shows:
00:02.0 VGA compatible controller: Intel Corporation Atom Processor 
D2xxx/N2xxx Integrated Graphics Controller (rev 0b)


and lspci -v shows:
00:02.0 VGA compatible controller: Intel Corporation Atom Processor 
D2xxx/N2xxx Integrated Graphics Controller (rev 0b) (prog-if 00 [VGA 
controller])
Subsystem: Intel Corporation Atom Processor D2xxx/N2xxx 
Integrated Graphics Controller

Flags: bus master, fast devsel, latency 0, IRQ 29
Memory at 4010 (32-bit, non-prefetchable) [size=1M]
I/O ports at 20d0 [size=8]
[virtual] Expansion ROM at 000c [disabled] [size=128K]
Capabilities: [d0] Power Management version 2
Capabilities: [b0] Vendor Specific Information: Len=07 
Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
Kernel driver in use: gma500
Kernel modules: gma500_gfx

Looks like the on-board video adapter shares main memory with the CPU. 
Linuxcnc system requirements says this is a no=no.


Question:  Will installing a PCI video card likely to reduce the latency 
and eliminate the warnings?


Tom Dean


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