Results of latency test, list of computers tested for use with LinuxCNC
07 Apr 2024 15:40 #297750
by tommylight
Replied by tommylight on topic Results of latency test, list of computers tested for use with LinuxCNC
Looking good! 
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20 Aug 2024 05:07 #308188
by uugp
Replied by uugp on topic Results of latency test, list of computers tested for use with LinuxCNC
I bought a few very old motherboards for $5-$10 to run CNC, which is much cheaper than the Raspberry Pi.
Post a test record, which I think this is a configuration that can work stably, for reference.
Configuration 1: ASUS-M4A88T-M with built in paralletport+AMD640iiX4+ATI graphics old card + RTAI.
Latency test 3 hours, seems to be good, but it is fake.
In order for the parallel port-stepping configuration to work stably, this value needs to be set to more than 9000 in setpconf, otherwise there will still be rare random errors, such as following errors or latency spikes.
The built-in graphics card can be used and without spike, and adding a graphics card can reduce the Latency slightly and obtain a good color, But once add a graphics card, it will have spikes issue. - no matter how much Latency value is set, so it must be add a option to GRUB: radeon.dpm=0
Several key points:
in GRUB:
radeon.dpm=0 Causes GPU to overheat
idle=poll Causes CPU to overheat
in BIOS:
CPU Over Voltage <= 1.25V Otherwise, it will overheat and crashes
ACPI APIC surpport = Enable Otherwise, Linuxcnc crashes with the RTAI kernel
others, as far as possible set Manuall or Fixed value
A confusion
on AXIS GUI graphical display area, LEFT click will causes the rolling coordinate numbers to be halt/pause update.
no interference with machine moving.
Post a test record, which I think this is a configuration that can work stably, for reference.
Configuration 1: ASUS-M4A88T-M with built in paralletport+AMD640iiX4+ATI graphics old card + RTAI.
Latency test 3 hours, seems to be good, but it is fake.
In order for the parallel port-stepping configuration to work stably, this value needs to be set to more than 9000 in setpconf, otherwise there will still be rare random errors, such as following errors or latency spikes.
The built-in graphics card can be used and without spike, and adding a graphics card can reduce the Latency slightly and obtain a good color, But once add a graphics card, it will have spikes issue. - no matter how much Latency value is set, so it must be add a option to GRUB: radeon.dpm=0
Several key points:
in GRUB:
radeon.dpm=0 Causes GPU to overheat
idle=poll Causes CPU to overheat
in BIOS:
CPU Over Voltage <= 1.25V Otherwise, it will overheat and crashes
ACPI APIC surpport = Enable Otherwise, Linuxcnc crashes with the RTAI kernel
others, as far as possible set Manuall or Fixed value
A confusion
on AXIS GUI graphical display area, LEFT click will causes the rolling coordinate numbers to be halt/pause update.
no interference with machine moving.
Attachments:
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21 Aug 2024 08:33 #308268
by seuchato
Replied by seuchato on topic Results of latency test, list of computers tested for use with LinuxCNC
uugp
Nice find! Those values are very good, almost too good to be true! If however those values are true and at 9000 there are no random latency issues anymore, then you do have a very nice system for software stepping, too.
Kindly allow a couple of questions / remarks / recommendations:
chris
Nice find! Those values are very good, almost too good to be true! If however those values are true and at 9000 there are no random latency issues anymore, then you do have a very nice system for software stepping, too.
Kindly allow a couple of questions / remarks / recommendations:
- Did you run any other program? I see 10 glxgears, but what about a browser, vimeo or youtube, ... while doing the latency test?
- On board graphics is usually the way to go. Tracking down and elimination sparce spikes is a hard job, usually also with questionable success. So I'd stick with onboard graphics.
- What do you mean by "... and obtain a good color ..."?
- Seems the mobo is for Athlon IIX* cpus, which appeared around 2009. So, really old . I'd check the capacitors before making chips and/or have a spare one available. Not sure if such an old mobo is really a good idea as a cnc controller though.
chris
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