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Thread: Guidance for Updated G0704 Electronics Design

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    Default Re: Guidance for Updated G0704 Electronics Design

    Quote Originally Posted by DJEkim33 View Post
    The link I sent was specific to using the Gigabyte board with the J1900 in it.
    I did see on some of the forums that the Gigabyte motherboard combined with a J1900 processor gave great latency results. The problem is that those motherboards are impossible to find unless you want to pay the 10x ransom price for the few that are in stock ($800+). Here is a good question, since I would need to isolate down to one core (out of the 4 present in the J1900), wouldn't the J1800 (dual core) processor give similar latency results? I can find some deals on a Gigabyte motherboard with J1800 integrated processor.

    If anybody knows of a reasonable price for one, or even a built up computer using one, I'd be interested in the link. It's too bad that Gigabyte doesn't offer the GA-J1900N-D3V anymore. That would allow a guy to have a full size PCI card installed as well.

    JJ



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    Default Re: Guidance for Updated G0704 Electronics Design

    Quote Originally Posted by JJ0704 View Post
    I did see on some of the forums that the Gigabyte motherboard combined with a J1900 processor gave great latency results. The problem is that those motherboards are impossible to find unless you want to pay the 10x ransom price for the few that are in stock ($800+). Here is a good question, since I would need to isolate down to one core (out of the 4 present in the J1900), wouldn't the J1800 (dual core) processor give similar latency results? I can find some deals on a Gigabyte motherboard with J1800 integrated processor.

    If anybody knows of a reasonable price for one, or even a built up computer using one, I'd be interested in the link. It's too bad that Gigabyte doesn't offer the GA-J1900N-D3V anymore. That would allow a guy to have a full size PCI card installed as well.

    JJ
    Actually they (J1900 MBs) are easy to find (at least in the USA)

    https://www.newegg.com/Product/Produ...-513-_-Product

    https://www.newegg.com/Product/Produ...-497-_-Product

    or the newer equivalent of the J1800

    https://www.newegg.com/Product/Produ...-726-_-Product

    or 4 core version:
    https://www.newegg.com/Product/Produ...-728-_-Product
    https://www.newegg.com/Product/Produ...-728-_-Product


    And as I said before isolcpus is a BAD idea if you are not running a parallel port system,

    All these tricks to lower latency are important on parallel port systems where your maximum step rate
    is determined by your maximum latency. This is not the case when you have an external stepgenerator
    and only need a 1 KHz thread. In this case isolcpus will do nothing but slow your system down

    Last edited by PCW_MESA; 07-23-2017 at 08:28 PM.


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    Default Re: Guidance for Updated G0704 Electronics Design

    Quote Originally Posted by PCW_MESA View Post
    Actually they (J1900 MBs) are easy to find (at least in the USA)
    Yes, but those are not 'Gigabyte' brand motherboards, which supposedly provide the low latency.

    Quote Originally Posted by PCW_MESA View Post
    And as I said before isolcpus is a BAD idea if you are not running a parallel port system,
    I will not be, and that's why I won't kill myself to find the magic Gigabyte J1900 processor combo. I will likely just settle on a value priced simple system.

    JJ



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    Default Re: Guidance for Updated G0704 Electronics Design

    Quote Originally Posted by JJ0704 View Post
    Yes, but those are not 'Gigabyte' brand motherboards, which supposedly provide the low latency.


    I will not be, and that's why I won't kill myself to find the magic Gigabyte J1900 processor combo. I will likely just settle on a value priced simple system.

    JJ

    I have both Gigabyte and ASRock J1800 and J1900s plus a ASRock J3355 and I have not noticed any significant latency
    difference between them. There really are no "magic" motherboards, especially with Preempt-RT. Most Motherboards will work
    but there are occasional bad ones (and Laptops are often "bad" due to power management traps that cannot be disabled)



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    Default Re: Guidance for Updated G0704 Electronics Design

    Quote Originally Posted by DJEkim33 View Post
    Interfacing the C35 to the 7i76e will require firmware I believe and maybe a bigger headache than you think for someone learning linuxcnc.
    Great advice. I am going to ditch that idea.

    Quote Originally Posted by DJEkim33 View Post
    So no core isolation and if the OP is dead set on using a 7i76e than he will need to change the kernel which is one thing he was trying to avoid. Changing the kernel is easy enough though if he still wants to go that route.
    Well, I suppose I need to get smart on changing the kernel...here I thought all computers ran in 'real time'. This is good info.

    Quote Originally Posted by PCW_MESA View Post
    In addition, Preempt-RT which is needed for Mesa Ethernet cards generally runs better on faster CPUs so a J1800/J1900 or the newer
    N3355/J3455s are _much_ better than a (painfully slow) D525
    That definitely opens up more options for motherboards/processors...and I am starting to think about maybe just building one of these mini-ITX form factor computers to keep it small.

    Quote Originally Posted by PCW_MESA View Post
    And as I said before isolcpus is a BAD idea if you are not running a parallel port system,
    Sorry. Failure of reading comprehension 101 on my part. I think I'm starting to get a better sight picture for the setup I am going for, and surprisingly I think it might be less finicky than I first imagined.

    Quote Originally Posted by PCW_MESA View Post
    If using a Mesa Ethernet interface card, I would start with the new LinuxCNC Debian Stretch test ISO:
    Index of /testing-stretch-rtpreempt
    Since this ISO has the uspace version of LinuxCNC and the required Preempt-RT kernel already
    Thank you for the link...this is very critical information for my setup!

    I am going to document all of my lessons learned in this journey so that maybe someday I can try a feeble attempt at a build thread titled "CNC Converting a G0704 with LinuxCNC for Dummies Like Me".
    v/r,
    JJ



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Guidance for Updated G0704 Electronics Design
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