Latency test "limits of abuse" question

More
11 Apr 2010 02:38 #2568 by crochambeau
Hello,

1.25 ghz Athalon (If memory serves)
1 GB ram
Matrox G400/450 video card

I've a fresh install of 8.04/EMC2, and am at the point of watching my latency. I'm instructed to abuse the computer, while not running EMC, easy enough..

The problem is that I've stumbled across some latency figures in the 2,200,000 range, which, as I understand it, voids the usability as a reliable machine.

That said, I've done stuff I never intend on doing with this machine in a CNC environment. Launching Pidgin IM configuration (while not connected to the internet); accessing a .doc file on a windows formatted slave drive (first launch of office on this machine), and I've also made it into the high 600,000 range playing audio. Though, it also gave me a latency spike when I moused to Applications > Office (clicking "Office" not an app), launched a Help file or started GIMP.

I've since uninstalled office applications (save Evolution which has some co-dependency currently), and disabled audio in BIOS. The additional windows drive is fated for a dusty drawer.

My current numbers (running for over a half hour) are:

Servo Thread 13262
Base Thread 14570

I've played with window sizing, launched about and help files, messed with absurd calculations on the calculator, run a hardware analysis, took a screenshot, started GIMP again and other mild mannered things, those numbers are holding.

Should I be concerned with the extremely high readings I got right out of the gate? Running latency is pretty much the first thing I did after install. The machine in question is not hooked up to the internet, so no updates have been installed. The .iso OS was downloaded yesterday.

Please Log in or Create an account to join the conversation.

More
11 Apr 2010 03:05 #2569 by crochambeau
Replied by crochambeau on topic Re:Latency test
Update: running glxgears ramped Base thread up to ~16K, until I moved my terminal window which gave me around 1,750,000 latency figures for both Servo and Base.

Is this normal, easily fixable or am I shopping for a new machine?

Please Log in or Create an account to join the conversation.

More
11 Apr 2010 11:22 #2575 by BigJohnT
Replied by BigJohnT on topic Re:Latency test
There are a couple of links on the Latency Test page on the wiki that I would try first. Are you using onboard video?

wiki.linuxcnc.org/cgi-bin/emcinfo.pl?Latency-Test

John

Please Log in or Create an account to join the conversation.

More
11 Apr 2010 15:42 #2578 by crochambeau
Thanks for your reply! The video card is an AGP, mobo doesn't have onboard video. Though I still haven't tried all the options in bios as to how video is handled. I presume sharing memory is bad, and will make sure that my selections reflect that philosophy.

I'm about to dig into that machine and remove any hardware not crucial to operation, I'll take note of exactly what's there, etc.

I'm inexperienced in CNC, and still cutting my teeth on Linux, so I thank you in advance for putting up with my growing pains.

Please Log in or Create an account to join the conversation.

More
11 Apr 2010 17:46 #2580 by crochambeau
It *may* have been my Matrox card, after stripping superfluous hardware and juggling the RAM didn't get results I tried an old 8MB ATI card. Couldn't force the latency spike like before, I'll report my findings in 24-36 hours and perhaps add my installation to the list. The card didn't seem to be acting up in any other ways, but it was plucked from an open bin (heap of cards) at a computer recyclers, so who knows what sort of ESD abuse it has been subjected to.

MoBo is a Soyo Dragon KT333, FWIW.

Please Log in or Create an account to join the conversation.

More
12 Apr 2010 11:32 #2587 by BigJohnT
It's good that your taking the time to do this step by step as it will benefit you later on during the integration of your machine. I see far too many that want to go from 0 to 100 and bypass all the steps in the middle.

What kind of machine are you building or converting?

John

Please Log in or Create an account to join the conversation.

More
12 Apr 2010 12:38 #2590 by crochambeau
Thanks John!

I'm scratch building a small moving gantry 3 axis, right now I'm figuring on 24x36x6 inches of movement. Primary purpose is going to be milling printed circuit boards and making nice holes in enclosures and 19 inch rack panels, I expect I'll wind up doing some small scale woodwork such as cutting dovetail joints and so forth as well.

As it turns out, I should have my drivers in hand by mid week, which will complete my control side of things, so getting the computer nailed down does have a sense of urgency. My hope is to have shaken the electrical bugs out and familiarized myself with the program a bit before engaging any automated tools. I'd rather break one thing at a time :P

I'm happy to report that the computer has held the following since my last post:

Servo max: 1007248 jitter: 10851
Base max: 39060 jitter: 14756

Please Log in or Create an account to join the conversation.

More
12 Apr 2010 12:56 #2594 by BigJohnT
Looks like your on the way...

If you use a jack shaft to connect both sides of the gantry it does simplify things like homing a lot.

John

Please Log in or Create an account to join the conversation.

More
21 Apr 2010 17:22 #2648 by andreas59
Replied by andreas59 on topic Re:Latency test
Maybe it will be helpful for others. I had a similar problem with my athlon 2000+ machine.
On this machine it was the ide busmaster (software)raid. I disabled it and used the normal ide
and was on the right way.

Please Log in or Create an account to join the conversation.

More
23 Aug 2010 08:34 #3848 by waynerod
Hey guys..

I'm kinda new to EMC2.. I've been fiddling with it on and off for about a month now.

I'm doing a 3 axis CNC Milling Machine for a school project (a subject called "Systems Engineering"). Its gone pretty well.. :laugh:

see if u can view the pic attached:

but... I've got a major concern .. The "latency test" :(

I'll try showin u the pic: (attached)

I'm getting the following:

Max Interval (ns) Max Jitter(ns) Last Interval(ns)
Servo thread(1.0ms): 4860389 3863884 997262
Base thread(1.0us): 3893902 3869597 24317



On this computer, I'm running it via LIVECD. (Ubuntu 8.10 aka Hardy)

I tried running it on my laptop (which Ubuntu is installed on) and get slightly worse results
where Max Jitter(ns) of Servo thread is 7730000. I don't intend on using my laptop for it.

I don't wanna get a new computer. Also, its not in my power as it is the school's. I managed to get this one as it is, with heaps of effort and pleading.


What I don't understand is... when I run the motors via "stepconfig", they run fine. I haven't tested out CAD stuff yet.... :unsure: So will I still be able to use the computer??


P.S. I'm new to the forums as well (in fact I just joined today), so plz go easy on me. It would be awesomely helpful if answers were explained simply.

Thanks,
Wayne Rodrigues.
Attachments:

Please Log in or Create an account to join the conversation.

Time to create page: 0.765 seconds
Powered by Kunena Forum