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- Just discovered my latency is through the roof, looking for a new ITX MB
Just discovered my latency is through the roof, looking for a new ITX MB
- B.Reilly01
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13 Aug 2020 21:01 #178136
by B.Reilly01
Replied by B.Reilly01 on topic Just discovered my latency is through the roof, looking for a new ITX MB
So before I removed LinuxCNC, I ran another jitter test, and let the screensaver turn on. Nothing else running. I don't think this PC is saveable. i.imgur.com/G2FAPMH.png I think that's 20ms of jitter... At this point, I'd rather just replace the PC that's choking just to run Linux and is quite old.
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13 Aug 2020 21:24 #178139
by tommylight
Replied by tommylight on topic Just discovered my latency is through the roof, looking for a new ITX MB
Screen saver must be disabled, everything power saving must be disabled.
You can try:
-boot from a USB stick and test latency by using both versions of LinuxCNC ISO's on the download page. If the latency is much better from USB, the hard drive is failing badly, so getting an SSD might save the PC.
-Remove all memory modules and insert them one by one, so insert only one module and boot from USB or hard drive - test latency 0 shutdown- rinse and repeat.
-Remove the CPU cooler and clean it and the CPU properly, put some thermal paste on the cpu and reseat the cooler.
You can try:
-boot from a USB stick and test latency by using both versions of LinuxCNC ISO's on the download page. If the latency is much better from USB, the hard drive is failing badly, so getting an SSD might save the PC.
-Remove all memory modules and insert them one by one, so insert only one module and boot from USB or hard drive - test latency 0 shutdown- rinse and repeat.
-Remove the CPU cooler and clean it and the CPU properly, put some thermal paste on the cpu and reseat the cooler.
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14 Aug 2020 02:44 #178148
by B.Reilly01
Replied by B.Reilly01 on topic Just discovered my latency is through the roof, looking for a new ITX MB
Booting from USB Stick stabilized the performance, though the latency was still 100,000ns. I'm going to try an SSD with the RTAI kernel tomorrow. Does the RTAI kernel always result in poor screen resolution? I'll also be replacing the RAM, since it's cheap to do.
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14 Aug 2020 07:22 #178169
by tommylight
Replied by tommylight on topic Just discovered my latency is through the roof, looking for a new ITX MB
That is usable, if there are no excursions .Booting from USB Stick stabilized the performance, though the latency was still 100,000ns.
Very often, but not always.Does the RTAI kernel always result in poor screen resolution?
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14 Aug 2020 23:31 #178213
by B.Reilly01
Replied by B.Reilly01 on topic Just discovered my latency is through the roof, looking for a new ITX MB
New SSD and 8gb of Ram and I'm running very stable, at 100,000 ns of latency. I'm not running the RTAI kernel, it's giving me fits installing. Do I need to replace LinuxCNC for the RTAI kernel to work? That's where my biggest problem has been, as well as 600x800 resolution on a 17in touchscreen... looks bad. I'm not doing software stepping, but am running fast rapids through the Mesa 5i25 card (hoping for 400ipm rapids).
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14 Aug 2020 23:43 #178214
by PCW
Replied by PCW on topic Just discovered my latency is through the roof, looking for a new ITX MB
100 usec of latency should be fine if you have hardware step generation.
If you use 5I25 firmware with the DPLL module, even 500usec of latency
would not be harmful.
If you use 5I25 firmware with the DPLL module, even 500usec of latency
would not be harmful.
The following user(s) said Thank You: seuchato
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15 Aug 2020 01:42 #178222
by B.Reilly01
Replied by B.Reilly01 on topic Just discovered my latency is through the roof, looking for a new ITX MB
It's actually an analog servo system, not sure how that stacks up with latency vs hw step generation. It needs to process quadrature feedback fast enough to adjust the analog outputs. The last system had serious issues with locking up and general instability. It appears either the harddrive (which was failing) or the ram was the cause.
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15 Aug 2020 02:19 #178225
by PCW
Replied by PCW on topic Just discovered my latency is through the roof, looking for a new ITX MB
The DPLL also helps with encoder reading as it samples the encoder count
with minimum jitter (typically less than 1 usec) so if you have a 1 ms servo thread, 500 usec or so of jitter is OK if you have the DPLL, 100 usec or so is OK without
with minimum jitter (typically less than 1 usec) so if you have a 1 ms servo thread, 500 usec or so of jitter is OK if you have the DPLL, 100 usec or so is OK without
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