Latency mesage SOLVED !

Waiting for upgrade with 2 SO-DIMM 1866MHz 4Go Cl11 and 1other SSD 250Go.
I have fixed the latency and setup Stepconf to get 60kHz step pulse.
Now I can run LC without any latency message.
In this video ou can see It running « not in simulation »

This video is 8’ long only 4 are useful.

Thanks for all the info on the ASRock motherboard. I bought one and it is working great for me now. For latency I'm getting 12us base and 9us on the servo thread, but I'm using the onboard graphics. I'm running the Wheezy RTAI.

Nove of the BIOS settings seemed to have much effect on the latency. ISOLCPUS=1 had a big effect. Also going from one 4G memory sticks to two 4G sticks made a big improvement too.

Thanks pdxalz for sharing your experience. I make a lot of test with the PC and it became unstable. I get some doubts about this mother board but you give me the good reason to find the solution.

On the hardware I change the SSD WD Green, to the faster SSD Crucial MX500 250Gb.

I make a clean install from scratch of LinuxCNC 2.7.15 on Debian 7 RT-Preempt
I change only few things on OS :
- GRUB- pulseaudio deactivated
- brltty deactivated (conflict with USB to R845 adapter for VFD)

With this configuration I get 13700ns max jitter.

I found the good settings for stepping. I can get up to 12000mm/mn feed rate. This is approximatively the maximum speed of stepper motors, 2400rpm.

Unfortunately, some times, at linuxCNC launch, I get latency message. But when it start correctly, LinuxCNC can ran for hours without any trouble.
I give you config files. If someone can found something wrong ?

Thanks tommylight for your patience and your help. It was a long way to get good results.
I have de computer that works perfectly with very good latency results (see here ). Now I can concentrate my self to the machine design and building.
I give the configurations files :