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After failing the latency test with 3 laptops, even after disabling auto update and power mgmt. , I installed the latest linuxcnc on a desktop.
About every 30 seconds the jitter goes from 8500ns to over 200000ns. So I tried ubuntu 8.04 and EMC2 but the same thing happens.
I tried Ispci-vv but I get "command not known". Am I condemned to buying PC's till I find one that works with linuxcnc or is there a cure.
The desktop I have is a IBM with a Pentium 4 Intel 828 IEB Ultra Chip. and 1 GB of memory.
Any help would be appreciated.
John.

Hi
You say you have installed the latest linuxcnc.
If you have installed from the 10.04 based live CD, you will
probably find it better to re-install the 8.04 based system.
That will work better on a P4 and you can still upgrade to linuxcnc 2.5.3

Then if you still get spikes in latency, do a lspci -vv ( LSPCI not ISPCI )
and then read my FAQs on latency at the head of the Computer section and
compare your chipset to the list of those requiring the smi fix

www.linuxcnc.org/index.php/english/forum...-the-latency-problem
www.linuxcnc.org/index.php/english/forum...me-latency-solutions

regards

HI ArcEye,
I had installed the latest linuxcnc from Linuxcnc.org. Right now I have 8.04 installed.
The latency problem happened with both . Finally managed to make lspci -vv to work
but not lspci.txt . I get "command not found". Probably something I am doing wrong.
Managed though to make screenshots from terminal. I will attach them.
Thank you for any help you can give me.
John.

Hi

but not lspci.txt . I get "command not found".

It is not a command. lspci -vv is command to list pci devices and -vv means at max verbosity (detail)
> lspci.txt means direct output to a file called lspci.txt

So running lspci -vv > lspci.txt should produce nothing at the command line but a file called lspci.txt will be created in the current directory containing the output

I have managed to piece together from the various truncated screenshots that you appear to have a 82801EB/ER rev02 chipset

If you read the additional post on the latency solutions FAQ
www.linuxcnc.org/index.php/english/forum...me-latency-solutions
you will see that I specifically mentioned this chipset.

It does not have the SMI problem, but exhibits similar behavior unless you turn off all power management, hyperthreading and set the fan to full speed all the time.

Read the post and then go into BIOS and locate and set the various options accordingly and hopefully it will stop the spikes

regards

HI,

I set the Fan to always on.

In Bios under "Power" there is a setting called " APM Bios Mode" Which I disabled. I hope that's Power Mgmt. That also disabled

Standby Timeout---30 min. and Hard Disk Timeout.

There is also "ACPI Bios IRQ----IRQ9 and ACPI Standby Mode----S3 both I left as they were.

There is also under "Power" Low Power Entry Activity Monitor

Low Power Exit Activity Monitor

Automatic Power On

These 3 settings can't be changed.

Hyperthreading I believe does not apply to this P 4.

Do you think there is anything else I can try?

Hi

The exact options you have will vary according to BIOS make and version

ACPI is Advanced Configuration and Power Interface , there should be an option to disable it, do it
You don't want to mess about with IRQs though.

If you can disable standby timeout and HDD timeout, do it too.
The last thing you want in the middle of a long gcode run, where there is no disk activity because it is all in memory, is the HDD shut down and the computer trying to go into 'sleep' mode.

Likewise you don't really want a BIOS option to shut down the screen (or even a screensaver)
The computer will spend long periods without any HID events (mouse, keyboard) and these management systems take that as a no activity, no need for a display cue.
Suddenly you will lose the plot dislay and may even have to switch the monitor on again to get it back

With a lot of these things, especially fan control, it is the monitoring that causes the problems, every 30 -60 seconds, interrupting other processes to check the processor temperature for example.

Once done, do another latency test and hopefully you will have an improvement

regards

johannbuck wrote:

Do you think there is anything else I can try?

one think i recursively do, is to spend several hours behind this type of problem, later i bang my head and keep me asking it is really worth or i have to drop a few bucks in a less dated computer, and have the machine running in short time.
Regards
Rick

Blackwind wrote:

johannbuck wrote:

Do you think there is anything else I can try?

one think i recursively do, is to spend several hours behind this type of problem, later i bang my head and keep me asking it is really worth or i have to drop a few bucks in a less dated computer, and have the machine running in short time.
Regards
Rick

Unfortunately, less dated and low latency are not synonimous, or you could just go out and buy the latest computer and everything would be hunky-dory.

The P4 computers I have, that have this chipset, will return 9K base thread heavily loaded, 5K lightly loaded
If you don't turn off all the power management however , they have 200K spikes every 62 seconds.

This was something I only discovered when the BIOS backup battery on one of them failed and BIOS reverted to defaults

It is worth a bit of effort to try to get it working, but yes after a point it becomes more fruitful to go for something like the D525 and equivilents, see other recent posts re that.

regards

Nothing worked with this Desktop, so have given up on it.

I started to experiment again with an old Compaq nc6120 that I have and finally some success.

In that Bios I found what to disable. It's called "Intel Speedstep Technology" and "Intel Execution Disable".

Disabling either one will give me sub 10000 ns jitter. Disabling both gives me around 7300 ns.

The only problem I encountered was that the fan stopped running despite having set the fan to be

always on. So I set the Laptop on top of a powerful fan and run latency test and glxgears for several hours.

I'm going to look into another old Laptop I have and see what I can come up with.

Thank you ArcEye even though I had no joy with the Desktop You encouraged this PC noob to explore further

and I'm learning a lot in the process.

The only problem I encountered was that the fan stopped running despite having set the fan to be
always on.

You could resolve that simply by jury-rigging it to the appropriate feed and it will run whenever the PSU is on.
(I hesitated to say 12v, because it could be less, need to check the rating first)

Shame about the other desktop, but the BIOS does sound completely different to mine.

regards