Asrock Q1900B-ITX

Old thread but still useful.

I need to replace the old controller pc (Fujitsu Amilo D8830, P4 laptop) and bought this board.
Tested with Chieftec 120W CDP-120ITX power supply and single 4G DDR3L ram from an old laptop with the old live usb.
Latency test with 12x glxgears, youtube playing some 4k video (didn't check stream size) and top on 1920x1200 display gives
servo thread: ~16000
base thread: ~26000

These started with ~2500, ~2500 and ramped up while starting more load.

These are about half of the values with the Fujitsu (no wonder, it's still a laptop even it has the same cpu as desktops).
And a little worse than the other controller I'm using (old Dell GX270 P4 with Radeon 9200 agp).

Really good board with this ~2 hour first test. Let's see what happens while testing overnight.

These started with ~2500, ~2500 and ramped up while starting more load.

I have had two of these running production LinuxCNC parport systems since 2017 on an worst-case-observed base thread latency of 14457. I configure conservatively for 20000, and have not seen a single event of the dreaded "unexpected realtime delay" message in all that time.

These boards for running LinuxCNC are (were) ideal. Currently produced and available from NewEgg or Amazon, 10W power fanless operation, fits in a 1U rackmount case, built-in parallel port, low latency, no Intel ME hazards. I don't know of any other motherboard on the market that fits the requirements.

I've been hoping for someone to update this evaluation for the newer ASRock motherboards in current production. Late last year the Q1900B-ITX seems to have disappeared from availability. ASRock appears to be producing later models currently. The ones with "...B-ITX" in the model number are the ones with built-in parallel ports.

Then you have a better board

Overnight test reached a about 16000 on both latencies with 6x glxgears and youtube.
This was with noirqbalance boot settings but without isolcpus. Maybe I'll buy another to wait for the next old pc to give up...

16k latency is good, but less is always better Can you share your settings ?
And maybe the ram has some impact also... have to test.

I'm using Asrock J4205-ITX as my home server/nas and it didn't work with the normal linuxcnc live image.

Also tried a smaller Mitac PD14-RI N3050 board. Display issues (only blank screen) with normal live and bad latency with preempt dev live.

I believe the newer J4xxx require more recent kernel and X display driver.

A bit more testing with every memory I had in hand.
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

It seems that this board likes to have 2 identical memory modules, there is quite big difference between the best and the worst values.
Hope this helps, maybe even with other boards too. Corsair is 1.5V version and the others 1.35V, bios setting for memory voltage was in auto setting.

My brother told he has some smaller 1G/2G modules, I'm going to test them too...

Hope this helps, maybe even with other boards too. Corsair is 1.5V version and the others 1.35V, bios setting for memory voltage was in auto setting.

Yes, that's a very valuable discovery and survey you've made: sensitivity to memory module variety. I had not even considered this as a significant factor with latency.

My "happily performing" systems all employ a single "Kingston Technology 4GB 1600MHz DDR3L PC3-12800 1.35V Non-ECC CL11 SODIMM Intel Laptop Memory KVR16LS11/4" module. This choice was not based on anything but "it's known to work in general applications (i.e., not LinuxCNC) of this motherboard, fairly priced, and available".

However with the BIOS setting for memory I am cautious to set to "manual" to match the hardware, not "auto".

My wish is that linuxcnc.org should inform a reliable baseline reference recipe for a PC parport system from scratch out of commodities you can conveniently "Buy Now" (for Now = today). We might call these live hardware recipes the "warrant" systems. The wiki articles are informative, but there's no definitive reference to current commodities. Identify what available parts you can buy today that require no art, experimentation, or drama on the part of the machine builder to achieve, other than normal PC assembly techniques. This is a matter of responsible curation, not commercial promotion. In 2017, this forum thread was the closest thing to that current information I could find at linuxcnc.org.

Richard J Kinch wrote:
My wish is that linuxcnc.org should inform a reliable baseline reference recipe for a PC parport system from scratch out of commodities you can conveniently "Buy Now" (for Now = today).

Literally any DELL Optiplex series with a Pentium 4 or Pentium D, Core, Core2Duo.
Price from 10 to 100 $. Plenty of them on sale, they never fail.