On Mon, 16 Feb 2015, Kirk Wallace wrote:

> Date: Mon, 16 Feb 2015 17:55:34 -0800
> From: Kirk Wallace <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
>     <[email protected]>
> To: [email protected]
> Subject: Re: [Emc-users] Mesa boards and latency
> 
> On 02/16/2015 04:26 PM, Jim Connery wrote:
>> Hi, If I use a mesa 7i92 do I still need to wory about latency? Will
>> using the mesa board improve my latency? I am planning on using a
>> ASUS X200MA-RCLT08 that has a Celeron n2830 processor. This also has
>> a touchscreen.
>
> These have good latency,
> http://www.ebay.com/itm/281497643572
>
> and you can keep your laptop free while machining.
>
>
> -- 
> Kirk Wallace
> http://www.wallacecompany.com/machine_shop/
> http://www.wallacecompany.com/E45/



That would be my general advice as well, The Baytrail Celerons have decent 
latency with Ethernet and Preemt-RT/Linucnc-uspace (which are needed to run 
the 7I92) The N2830 seems similar to the J1800 desktop processor which is fine 
with the 7I92 at 1 KHz but laptops and notebooks often have quite agressive 
power management, and often some of it cannot be disabled.

That said, depending on what you are doing, even a system with fairly lousy 
latency might be made to work by lowering the servo thread rate to say 500 Hz

HostMot2 configurations have a mechanism that allows a fair amount of 
tolerance to jitter (a DPLL that syncs to linuxCNC access rate and samples
critical signals with most of the jitter removed) so on a 1 KHz servo 
thread, a couple hundred usec of latency is fine but sometimes laptops
have latencies in the multiple mS region...

>
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Peter Wallace
Mesa Electronics

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