Latency Test: Large value for Servo Thread

Hello everyone,

I am trying to set up a nice box to control the milling machine I've ordered (stepcraft 420).

Running the latency-test I get "acceptable" values for Base Thread (~27000) but a huge jitter value for the Servo Thread (335000).
From what I see in the (Last interval) column, the threads are called late constantly (i.e. no single spike).
This happens with no load whatsoever on the machine.

The specs are:
CPU: Intel Pentium 4 CPU 3.00 GHz (single core, Hyperthreading turned off in BIOS)
2 GB of RAM
Software: Linux CNC 2.5.3 with Live CD

I suspected the on-board graphics to be the culprit and put a PCI Card into the box, but that did not change the values.

Any hints where I might look?

Thanks,
Robert

EDIT:
Just tried the Live CD which is based on Ubunto 8.04 and there I get reasonable goot values: When running glxgears max jitter values are 13.500 (Servo) and 23.370 (Base).
Seems odd that it is so much better with the older kernel though....

Hi

You should be using a UniProcessor built kernel (8.04) with a P4 not the SMP one (10.04)
27K is not 'acceptable', it is bordering unusable for a software stepping based system

The figures with 8.04 are not brilliant either however.

I suspected the on-board graphics to be the culprit and put a PCI Card into the box, but that did not change the values.

You might well be right but depends what card you put in. Putting a Nvidia or ATI card in might make things worse or give no improvement

I personally have used Raedon AGP cards to replace on-board graphics in P4s and they worked very well

Some background reading

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

regards

Looks like I've found a better box (on the heap of old boxes lying around in our office...).

This one has both values below 9000 with glxgears running.

Its an Athlon 64 X2 Dual Core 4200+, with 4 GB RAM and an nVidia Card, runnin under 10.04.

Looks like I've found a better box (on the heap of old boxes lying around in our office...).

This one has both values below 9000 with glxgears running

Good, life is too short to bother with lemons.

Its an Athlon 64 X2 Dual Core 4200+, with 4 GB RAM and an nVidia Card, runnin under 10.04.

Have you tested it running Axis?

Sometimes the nvidia cards with proprietary drivers cause problems with the heavy openGL usage in Axis, which does not show up just running glxgears.

The answer is normally to switch to the opensource nouveau drivers

regards

I already have nouveau running (It's the default when installing from the CD), and no reason to use the proprietary drivers from nVidia .