Mach 3 or Mach 4?

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acourtjester
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Re: Mach 3 or Mach 4?

Post by acourtjester » Tue Apr 20, 2021 6:03 pm

I went with the THCAD-10 as that is what Rod W had recommended from his build, and will use the THCAD-5 for the Ohmic sensor. Some images of the Hand truck controller as it sits today, still needs a handle and paint. I put a small holder on the back for a plastic box for Plasma consumables, and a place to wind the power cord.
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Buckmaster1967
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Re: Mach 3 or Mach 4?

Post by Buckmaster1967 » Wed Apr 21, 2021 2:55 pm

I have all my parts except the Mesa 7i96 ethernet control board, which is on back order at Mesa. Anyone have one for sale?

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Re: Mach 3 or Mach 4?

Post by robertspark » Wed Apr 21, 2021 3:16 pm

7i76e???

bit more expensive but more iOS

Buckmaster1967
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Re: Mach 3 or Mach 4?

Post by Buckmaster1967 » Wed Apr 21, 2021 9:58 pm

robertspark wrote:
Wed Apr 21, 2021 3:16 pm
7i76e???

bit more expensive but more iOS
What is the difference?

bevins
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Re: Mach 3 or Mach 4?

Post by bevins » Thu Apr 22, 2021 6:50 am

Hi guys, I want to comment on some of the posts here for linuxcnc.
Laptops are generally not recommended and not used with linuxcnc because of the native latency issues.

Also multicore will do you really no good in this arena becasue of the latency it introduces. Linuxcnc uses a realtime kernel and requires latency to be at minimum level and multi core computers induce latency when using multiple cores. Some have made them work but you may find you will have to shut down the multicore functionality of the motherboard to get to acceptable levels.

I just finished a plasma using linuxcnc and mesa boards. I used 7i92 and 7i76 with thcad for thc and ohmic sensing. The new QTplasmaC is amazing and works really well. Really well thought out and used solely for plasma.

I can post some videos of my machine I just finished.

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Re: Mach 3 or Mach 4?

Post by adbuch » Thu Apr 22, 2021 11:36 pm

I will look forward to seeing some of the photos of your new machine.
David

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Re: Mach 3 or Mach 4?

Post by robertspark » Fri Apr 23, 2021 3:03 am

can you still buy a single core machine?

multicore is fine with linuxcnc, it does improve performance, but some intel features you need to turn off which are supposed to be performance improvement features, but they mean that the timing is not consistent

the real-time kernel is about constant timing, things happening consistently at the same time, with little jitter (timing variance)

stuff like hyperthreading, c-states, or turbo frequency mean that the jitter goes haywire and is not consistent.

I would recommend that you buy a Mesa board to use with linuxcnc as this means that the timing is a little more flexible and you are only concerned with one timing loop ..... the servo thread which is a 1khz timing loop. this is because the Mesa hardware unloads the stepper pulses from the pc to the Mesa card.

the Mesa / linuxcnc guys don't like calling the Mesa cards motion controllers... but essentially that is what they are, they are fed data packets at a constant rate (1khz) and take care of the stepper motor step and direction signals (or your servo control too analog or whatever.... sorry I have no knowledge there)

I have s fanless 5500u pc which uses an i7 dual core CPU. I thought I would get good performance from it. (I actually bought it to upgrade from a fanless 3150n with additional comms ports rs232 and both have dual ethernet cards.

it works ok... but I probably could get marginally better performance with a quad core i5 (slower) instead of my dual core (faster) i7

..... but really it does NOT make much difference... just that the timing is consistent.

I had a problem with my fanless i7 5500u that required a little fiddling to get the issue sorted ..... it probably would not have been a problem if I used a "business" spec pc such as a Dell optiplex or an IBM / Lenovo thinkcenter

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Re: Mach 3 or Mach 4?

Post by robertspark » Fri Apr 23, 2021 9:44 am

single core / multi-core performance.

here is a live link (updated regularly) showing single core performance for CPU's for PC's.
https://www.cpubenchmark.net/singleThread.html

If you are keen on Centroid / Acorn machines (no they don't [currently] support plasma]) the centroid Acorn basically an addon module for a a beaglebone green. https://www.centroidcnc.com/centroid_di ... oller.html

The reason why I mention Centroid Acorn (which does not support plasma / THC (at present, that may change at some point). is because they only recommend compatible PC's which have a single core thread rating
1.) The PC CPU must have a SINGLE CORE minimum benchmark of 1500 for Milling Machines and Router, 1000 for Lathes You can look up a CPU’s benchmark # using this web site.

http://cpubenchmark.net/singleThread.html

Notice that this is the “Single Thread” benchmarks chart.
Using a CPU with a single thread benchmark rating higher than 1500 is required for Mills and Routers, 1000 and higher for Lathes.
https://www.centroidcnc.com/cnc_pc_perf ... ments.html

Unfortunately ... LinuxCNC is a little suck and see.... and no such "rating" is given....

below is my old N3150 compared to my current i7-5500u

https://www.cpubenchmark.net/compare/In ... 2470vs3042

I almost changed to a fanless i5-8250u and you can see the incremental single core performance despite it being a quad core (same as the N3150 and being 1.6ghz (same as the N3150) it actually has a 4x single core performance to the N3150 and ~ 18% better performance than the i7-5500u, despite the i7-5500u having a 2.4ghz core frequency (but only 2xcores). ... but I've since got a nice stable setup and fair latency with the i7-5500u and it meets my needs just fine for linux running a 7i76E AND a 7i92H off individual ethernet ports.

It should be noted that the i7-5500u only just meets the 1500 requirements of the Acorn Centroid for mills and routers at 1646.

Some guys are using Raspberry Pi 4 boards and some are using Odroid H2 Plus
https://www.odroid.co.uk/ODroid-H2
They do not have a very good (single core) rating, but they do have dual NICs (ethernet ports), but they are roughly double the performance of the N3150
https://www.cpubenchmark.net/compare/In ... 3042vs3679

Some of the really high core number AMD's have poor realtime performance for LinuxCNC + can be a problem with drivers / kernel version being too new.

Also avoid NVidia (and some ATI) graphics cards as they can add to the machine's latency and realtime (scheduled task) performance.

hope some of this waffle helps someone

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Re: Mach 3 or Mach 4?

Post by acourtjester » Fri Apr 23, 2021 11:04 am

Something a little off to the side after I converted a Dell Optiplex 790 SFF PC to only Linux and setup the Mint 20 network for the 7I78E I no longer had ethernet connectivity. I thought this would be a problem for getting upgrades or add on downloads. I had a Ultra Wireless USB adapter, plugged it in linux saw it and showed my WIFI network, plugged in the password and the internet was back to be used. I leave the USB adapter out if not being needed, happy as a clam again. :HaHa
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Re: Mach 3 or Mach 4?

Post by robertspark » Fri Apr 23, 2021 11:45 am

It is "generally" recommended that a wifi dongle is used for internet access, instead of using internal wifi adapters for internet conections. This is again because of latency issues. the USB devices are not so demanding on the processor at potentially causing interrupts and therefore affecting latency.

I say it is "generally" recommended..... but again in my experience .... it depends. I am using an internal wifi adapter which is a PCIE device and whether it was plugged in or removed made zero difference to latency {your experience may differ} hence I left mine in and use that.

if you install the debian linuxcnc install disk (not via mint) then you need to change the wifi adapter because if does not like to share the connection arrangement between the MESA card and the ethernet adapter. Its a simple software change via the terminal (aka command prompt in windows). just copy and paste / type the following commands into the terminal.

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sudo apt-get update

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sudo apt-get upgrade -y

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sudo apt-get install network-manager network-manager-gnome

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sudo apt remove wicd
I'd probably suggest restarting the machine at this point, so that your wifi is automatically restarted with network-manager as the WiCD icon will have changed its appearance. You can do it via terminal commands ..... but the big button / restart is usually easier.

Then run

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sudo apt autoremove -y
and it will clear out any remaining fragments of wicd scripts etc (you won't need them)
.
Then you can set up your internet connection and mesa wifi card. The mesa ethernet card will require a static IP address 10.10.10.10 is the recommended one... but you will need to change one of the jumpers on the MESA card.

once your static IP address is setup, I would suggest pinging your MESA card by typing the following into the terminal:

Code: Select all

ping 10.10.10.10
expect the numbers to be in the order of 0.02/0.03 etc.... or lower. if they are above or around 0.2 or 0.3sec then you will need to do other software changes to improve this (easy to do nothing complicated).

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