latency / SMI fixes for 2.8.2?

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10 Jan 2022 17:15 - 11 Jan 2022 17:34 #231323 by dbotos
I've got a fresh install with the following details:

Lenovo ThinkCentre M52 (8113-E7U)
P4 3.2 GHz 2 MB cache
1 GB RAM
82801GB chipset ICH7 rev 1 (one of the ones known for SMI issues)
hyperthreading and processor power management disabled in BIOS
Mesa 5i25, Mesa THCAD-300, and Gecko G540

latency test numbers (running two instances of glxgears and browsing the internet):

servo thread: 273,402 ns max jitter
base thread: 344,569 ns max jitter

The wiki ( wiki.linuxcnc.org/cgi-bin/wiki.pl?FixingSMIIssues ) mentions fixes for the RTAI kernel under Ubuntu.  The pinned FAQs in this sub-forum about latency are pretty dated (2012).  Are there any latency / SMI fixes to try for the PREEMPT RT kernel under Debian 10 (Buster)?

Thanks,
David
Last edit: 11 Jan 2022 17:34 by dbotos.

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10 Jan 2022 17:32 #231324 by dbotos
P.S. Currently running on-board graphics (read that a dedicated video card can sometimes help latency, but haven't tried that yet). Also, I noticed a "fan acoustics" setting in the BIOS, which I haven't messed with yet either (currently set to "normal"), but I did see some mention of people messing with fan/temperature settings in their BIOS.

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12 Jan 2022 14:28 #231568 by dbotos
Nevermind. I ordered a used Dell Optiplex 980 tower with an Intel Core i5-650 processor (a search revealed good latency results with that hardware). Life is too short and I've got too much $ tied up in the rest of my table to be fighting old hardware.

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13 Jan 2022 07:01 #231634 by tommylight
Sorry for the late reply, but you are right, for the price of older computers it just does not pay off to waste time.
So far i had luck with almost everything i tested, and there is a topic here with my findings for some of the stuff i can find localy, search for "latency tests older pc".
Never had a 980 though...

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13 Jan 2022 17:48 #231683 by dbotos
No worries. I ended up doing some general research about real-time OSes, latency, and system management mode / interrupts before deciding that messing with the old Lenovo was going to be an uphill (if not a losing) battle.

Hoping to make 2022 the year I get my plasma table going again. It started out being controlled by Mach 3, but then I decided to switch to LinuxCNC several years ago (which I did get my little laser module working on the same table with), then life happened, and here I am. Figured I might as well use the latest version and take advantage of the PlasmaC stuff.

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