LinuxCNC 2.7.3 Latency-Test strange results

Hi there,

I'm trying to install a bare minimum linuxcnc 2.7.3 on an old PC (about 17 years old Celeron 433Mhz+512Mb Ram) but i'm running into some problems. When I run latency-test I get some strange results. The base thread (25us) is running as low as 200ns instead of the expected 25000ns. I'm guessing RTAI is not working properly, but it's wild guess.

I'm not a linux expert so I'm hoping you guys can help me.

This is what I did:
1. Installed debian 8.2 netinst without any extras
2. added the linuxcnc repository to sources.list and updated aptitude
3.Installed the linux-image-3.16.0-9-rtai-686-pae and rebooted to the rtai kernel
4.Installed lightdm and lxde-core and rebooted
5.In lxde environment installed the linuxcnc-uspace

Any thoughts?
Thanks.

You should use standard LinuxCNC with a RTAI kernel not the uspace version of LinuxCNC

Also a 433 Mhz Celeron is likely to work better with an older OS, say Ubuntu Hardy (8.04)
so downloading the linuxcnc/ubuntu 8.04 live CD image is (IMHO) more likely to lead to a usable system

Thanks for the reply.
I thought I should use RTAI version but the repository for linuxCNC 2.7-rtai is empty.
I can only install linuxCNC using the uspace

I currently using the ubuntu 8.04 version (with linuxCNC 2.5.3), but by installing this "minimal" debian, I feel the PC is alot more "responsive". Don't know if the results of the latency test will show corroborate that.

Thanks!!

Ok.
I'll make one final try with Debian Wheezy "minimalistic" instalation and the RTAI kernel for it available at machinekit .
I've tried the Preempt RT version of Wheezy but when I run latency test the PC freezes completely.

EDIT:Actually I didn't realized that the linuxcnc repository for wheezy already add a rtai kernel. I'll try that instead.

-7º C now Thats cold. I have 19º and it's almost winter. lolol
I've managed to get the "minimum" wheezy+linuxcnc running on my PC. Although the OS is more responsive and feels more fast, the latency-test results are worse(about 40~50% more jitter) and linuxCNC crashes...

In ubuntu 8.04 - base thread jitter is about 19000ns
In wheezy - base thread jitter is about 30000ns

If you decide to try I did this:
Installed the netinst version without any options.
Installed the rtai kernel from linuxcnc repository
Installed lightdm and lxde-core (JWM is even lighter but it's too hardcore for me! )
Installed linuxcnc

NOTE: lapic is not active so I had to follow the instructions in linuxcnc doc to activate it on grub

I used StepConfig fine.
When trying to run linuxCNC it crashed.
I gave up on it (given the latency results) and returned to 8.04. I'll probably go has it is for now.