Asrock Q1900M: Unexpected Realtime Delay, but Good Latency Values

That makes sense.

Do you have any idea on how i could maybe debug what its stalling at?

What version of Linux, LinuxCNC and kernel?
uname -a
?

Well i figured this out, pretty strange but it turns out that there is a watchdog messege on dmseg that occures exactly every 1 minute and i had dmesg ouput on the serial port. Well apearantly this superio chip stalls when the serial port is used as anytime anything is written to that serial port there is a latency spike. Simply removeing the serial port console= line from the kernels cmdline fixed the issue.

So it would seam that on this machine writeing to the serial port blocks the parallel port for a bit, thats not too bad i can just use netconsole to monitor the system

Probably from using the same IRQ.
Thank you for reporting back.

I had an asrock Q1900B-ITX and it liked to have two identical memory modules. May also help with latency.

Test results (copied from here: forum.linuxcnc.org/18-computer/29224-asrock-q1900b-itx#128103 ):
Quick ~30-60min test with 6x glxgears and a hd video, only memory module(s) were changed between tests.
servo / base latency, ram
11035 / 11234 2x 8G Hynix HMT41GS6BFR8A-PB 1600 CL11
9380 / 11482 2x 8G Corsair CMSO8GX3M2A1333C9 1333 Mhz CL9
10747 / 12206 8G Micron MT16KTF1G64HZ-1G6E1 + 8G Samsung M471B1G73QH0-YK0
9886 / 17090 4G Micron MTBKTF51264HZ-1G6E1 + 4G Samsung M471B5173QH0-YK0
11618 / 17726 1x 8G Samsung M471B1G73QH0-YK0
11898 / 20126 1x 2G Ramaxel RMT3190ME76F8F-1600
11693 / 22918 1x 4G Micron MTBKTF51264HZ-1G6E1
10440 / 23242 1x 8G Hynix HMT41GS6BFR8A-PB 1600 CL11
11627 / 24188 1x 8G Micron MT16KTF1G64HZ-1G6E1
11257 / 28173 1x 4G Samsung M471B5173QH0-YK0 PC3L-12800S-11-12-B4
10107 / 28223 1x 8G Corsair CMSO8GX3M2A1333C9 1333 Mhz CL9


 

All PC's in probably last 10 or more years like to have 2 memory modules as they can all do dual channel communication.
Some Xeon's and AMD can evem do 4 channels.
And yes, more memory improves latency, so 8GB should be minimum and there is no reason to have over 16GB for Linux and LinuxCNC if used for machine control only.
When possible, always choose 2x4gb or 2x8gb.