Intel H81
- pmcstoneinc
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05 Sep 2014 23:56 #50817
by pmcstoneinc
Replied by pmcstoneinc on topic Intel H81
Same thing, will install but will just not boot, cursor on top left, I have and older PC, Shuttle brand as well and it boots with no issues, I am thinking it has to do with the display drivers, ie 4k uhd display, again thanks for all your help.
I will still use this pc/box for around the work place just wont be using it for LinuxCNC. I am trying to find a tiny pc with network compatibility to go with a Mesa network FPGA board.
I will still use this pc/box for around the work place just wont be using it for LinuxCNC. I am trying to find a tiny pc with network compatibility to go with a Mesa network FPGA board.
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03 Oct 2014 00:44 - 03 Oct 2014 00:47 #51735
by uli12us
Last edit: 03 Oct 2014 00:47 by uli12us.
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03 Oct 2014 01:01 - 03 Oct 2014 01:01 #51736
by PCW
Last edit: 03 Oct 2014 01:01 by PCW.
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- pmcstoneinc
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03 Oct 2014 05:00 #51740
by pmcstoneinc
Replied by pmcstoneinc on topic Intel H81
What you mentioned earlier worked Peter, sorry I have been all over the place lately with work. How do you like the PC? Lots of potential from such a tiny box.
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03 Oct 2014 22:03 - 03 Oct 2014 22:04 #51759
by PCW
If Preemt-RT changes the CPU clock frequency (or perhaps calculates it wrong),
thats probably due to a kernel bug with your specific hardware. I have never seen this behavior
and have run Preemt-RT on at least 10 different systems.
Latency in Preemt-RT is typically longer than RTAI or Xenomai because it works in a different way.
RTAI and Xenomai are dual kernel systems that run a special real time kernel that has Linux as one
of its tasks. The advantage of this is that the real time kernel is small and well defined (and designed from
the start for real time) so can have minimal latencies. One disadvantage of this system is the real time
kernel cannot use standard linux device drivers.
Preempt-RT uses a single kernel (in fact Preempt-RT is really a patch set that is applied to the stock Linux kernel source)
The patch set makes the kernel full preemptable so high priority tasks can preempt low priority tasks.
this allows use of normal linux drivers (such as Ethernet drivers) in a real time context. It does result in higher
latencies so may not be suitable for things like software step generation
thats probably due to a kernel bug with your specific hardware. I have never seen this behavior
and have run Preemt-RT on at least 10 different systems.
Latency in Preemt-RT is typically longer than RTAI or Xenomai because it works in a different way.
RTAI and Xenomai are dual kernel systems that run a special real time kernel that has Linux as one
of its tasks. The advantage of this is that the real time kernel is small and well defined (and designed from
the start for real time) so can have minimal latencies. One disadvantage of this system is the real time
kernel cannot use standard linux device drivers.
Preempt-RT uses a single kernel (in fact Preempt-RT is really a patch set that is applied to the stock Linux kernel source)
The patch set makes the kernel full preemptable so high priority tasks can preempt low priority tasks.
this allows use of normal linux drivers (such as Ethernet drivers) in a real time context. It does result in higher
latencies so may not be suitable for things like software step generation
Last edit: 03 Oct 2014 22:04 by PCW.
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05 Oct 2014 19:58 #51800
by uli12us
Good to know, that RT-preempt runs only on 1 kernel, anyway as much kernels are available.
In this case it should be better, next time I need a board for this purpose I buy one with less kernels, but higher clock rate.
But the H81 board have a latency of 8000, while the celeron Board with only 2/3 of the clock rate have a slightly faster latency of 7000.
In this case it should be better, next time I need a board for this purpose I buy one with less kernels, but higher clock rate.
But the H81 board have a latency of 8000, while the celeron Board with only 2/3 of the clock rate have a slightly faster latency of 7000.
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05 Oct 2014 21:55 - 05 Oct 2014 21:57 #51804
by PCW
For Ethernet/Preemt-RT faster is better and latency (as show by the latency test) is not very important (as long as its not greater than say 50-60 usec)
For a step/dir system that will run at 1 KHz servo thread CPU choice is not critical, but if you need the fastest servo thread you can get, CPU speed is important.
Also I think there's a language difficulty here, when I say kernel I mean a software construct versus a processor core
Both RTAI and Preemt-RT support multi-core processors, though there may be latency advantages to restricting the real time tasks to 1 processor
For a step/dir system that will run at 1 KHz servo thread CPU choice is not critical, but if you need the fastest servo thread you can get, CPU speed is important.
Also I think there's a language difficulty here, when I say kernel I mean a software construct versus a processor core
Both RTAI and Preemt-RT support multi-core processors, though there may be latency advantages to restricting the real time tasks to 1 processor
Last edit: 05 Oct 2014 21:57 by PCW.
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29 Dec 2014 10:34 #54355
by pmcstoneinc
Replied by pmcstoneinc on topic Intel H81
Thank you all for your insight into this, but I have come to the conclusion there is a lot of installing and modifying of drivers for the Shuttle DS81 to even work on any current distros. I seem to get a working system with Arch Linux or newer Ubuntu 14.04 but again lot of modifying of drivers to get the system actually stable. Back to the drawing board......
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