velocity feed rate is not correct on new computer

Hello,

I have been using linuxcnc successfully on a single core computer. In my program I moved a basket repetitively up and down for 30 seconds at 50 mm/sec with max_acceleration of 1000 mm/s/s. The distance that I moved is 10 mm one way. The traverse measured time is 0.2 sec one way. The period is 0.4 sec for one complete cycle 10 mm forward and 10 mm backward. 30/0.4= 75 complete traverse cycles. That is I ran 75 cycles, and I measured 30 seconds for time.

Recently I installed the same setup on a new dual cores computer. I changed to new latency time using the latency test.
After running the program, instead of getting the total time of 30 seconds above, I got around 34 seconds. On the old computer, I can
see the velocity bouncing around 3000 to 2600 mm/min when the machine moved 10 mm forward and backward. On the new computer, I see the velocity bounces between 3000 to 1xxx mm/min. As a result it took 34 seconds instead of 30 seconds after 75 complete traverse cycles. I am puzzled.

Please advice and thank you for your help,
Alex

What version of linuxcnc are you using?
Were they the same version each time?

Did you use the exact same config files?
You say you change the latency time - which to me implies you used stepconf to build the new config - is this true?
Was the latemcy better or worse on the second config?
In stepconf (AFAICT) changing the latency time will change the max velocity of the config.

Can you post config file? (preferably the before and after)

Chris M

Dear Chris,

On the working old machine with Ubuntu 10.04.4 it uses Linuxcnc 2.5.0.
On the new machine with Linux 7.9 Debian it uses Linuxcnc 2.7.0.

Yes, it is true that I used stepconf modifying only the latency on the old.stepconf to generate a new new.stepconf.
Old latency is 15000 and new latency is 17000 or worse. I have a third machine similar to second machine with 9600 but that did not help either.

Old and new stepconf files are attached. I will read up on AFAICT and I will see if I can downgrade the software to see if it is an issue.

Thank you kindly for your help,
Alex