Dell Dimension 3000 latency issues

JimS
Offline
Junior Member

04 May 2016 03:35 #74209 by JimS

Dell Dimension 3000 latency issues was created by JimS

Just starting into LinuxCNC and have latency issues in the 500,000 range. Trying to wade through the details of SMI, etc but not following much of it. I ran the jitter test from the live cd and had what looked like reasonable numbers. Around 25,000 as I recall. I loaded Ubuntu 12.04 LTS thinking that was a good choice but was just reading that 8.04 might be better than 10.x for older hardware. But much of what I read about SMI and such seemed very dated. So I am not sure how much of it still applies. tried to run setsmi but got some errors that kept it from running. This newbie needs some help....

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

JimS
Offline
Junior Member

04 May 2016 11:38 #74218 by JimS

Replied by JimS on topic Dell Dimension 3000 latency issues

Here is some information on the PC. I haven't changed any bios settings yet.

processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Pentium(R) 4 CPU 3.00GHz
stepping        : 1
microcode       : 0x9
cpu MHz         : 2992.514
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe constant_tsc up pebs bts pni dtes64 monitor ds_cpl cid xtpr
bogomips        : 5985.02
clflush size    : 64
cache_alignment : 128
address sizes   : 36 bits physical, 32 bits virtual
power management:

/proc/cpuinfo (END)

uname -r
3.4-9-rtai-686-pae

lshw -C display
  *-display               
       description: VGA compatible controller
       product: 82865G Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 02
       width: 32 bits
       clock: 33MHz
       capabilities: pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:16 memory:e8000000-efffffff memory:feb80000-febfffff ioport:ed98(size=8)

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

PCW
Away
Moderator

04 May 2016 15:34 #74231 by PCW

Replied by PCW on topic Dell Dimension 3000 latency issues

Before worrying about SMI or other exotica, I would make sure that all power
management/clock speed options are disabled in the BIOS

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

JimS
Offline
Junior Member

05 May 2016 02:50 - 05 May 2016 13:02 #74253 by JimS

Replied by JimS on topic Dell Dimension 3000 latency issues

Looked at settings in BIOS. Hyperthreading was already disabled. I disabled sound. There was a CPU speed option of "Normal" or "Compatibility". The description said Compatibility was "a lower compatibility speed setting which lets you accommodate speed-sensitive applications". I left it set to Normal.

I then ran the latency test from the 10,04 live CD. The numbers were very close to 25000 and 25000. (a 20x improvement!). I did the same thing with the 8.04 live CD. Almost the same: 25000 and 29000. I then repeated the test with the installed 12.04. Got around 500,000 as before.

It may be the the 12.04 install isn't optimized for LinuxCNC. This is an old machine with a CD drive (not DVD) so to get 12.04 installed I had to do an install of the OS and then install the real time kernel and then linuxCNC. So it is very likely something is not optimum. I could try to find an IDE DVD drive and install and then retry but I think I may just live with 10.04 and LinuxCNC2.5.0. I am open to ideas for newer version but I am not sure it is worth the trouble - I would welcome others thoughts on that.

I installed 12.04 as detailed in section 7.2 here:
linuxcnc.org/docs/html/getting-started/getting-linuxcnc.html

RAM on this PC is 1 Gig.

Last edit: 05 May 2016 13:02 by JimS.

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

Todd Zuercher
Offline
Platinum Member

05 May 2016 13:25 #74271 by Todd Zuercher

Replied by Todd Zuercher on topic Dell Dimension 3000 latency issues

There is no reason to stay with Linuxcnc 2.5 on Ubuntu 10.04. Versions 2.6 and 2.7 both work perfectly fine on it. Updating is as simple as changing or adding the repository address and running an update (if you have an internet connection). If you don't then you have to download the debs and install them some other way.

The following user(s) said Thank You: JimS

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

JimS
Offline
Junior Member

05 May 2016 13:43 #74273 by JimS

Replied by JimS on topic Dell Dimension 3000 latency issues

Thanks Todd. I did find the instructions on updating and good to know it works fine. Looks like I need to go to 2.6 and then 2.7.

Any compelling reason I should be trying to get to 12.04 rather than 10.04? It appears I won't be able to do any updates (other than LinuxCNC) on 10.04 and I am not sure how installing packages I might need will work or not work since support has ended. But I don't think I will be needing much more than what is already included. This is only going to be used for machine control.

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

Todd Zuercher
Offline
Platinum Member

05 May 2016 14:33 #74275 by Todd Zuercher

Replied by Todd Zuercher on topic Dell Dimension 3000 latency issues

Not that I know of, I think 12.04 is as much of a dead end as 10.4, as far as Linuxcnc is concerned. In fact I'm not sure that it even counts as being fully supported. Linuxcnc switched to Debian rather than go on with Ubuntu.

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

JimS
Offline
Junior Member

05 May 2016 15:19 #74276 by JimS

Replied by JimS on topic Dell Dimension 3000 latency issues

The time line I just looked up has support for 12.04 end late in 2017 (ubuntu support, not linuxcnc). They all end sometime but that is reasonably far off (IMHO). So no issues with loading a few packages I may find I need or want.

But I am not tied to Ubuntu. Should I be looking at Debian? Any issues with running the latest Debian version on an old P4? My understanding (which is very limited) is that 10.04 is a suggested OS for such a PC.

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

Todd Zuercher
Offline
Platinum Member

05 May 2016 16:12 - 05 May 2016 17:11 #74279 by Todd Zuercher

Replied by Todd Zuercher on topic Dell Dimension 3000 latency issues

It would likely work better than Ubuntu 12.04. The only P4 machine I currently have running Linuxcnc was installed using Ubuntu 10.04 years ago (started with EMC2 v 2.3) and is currently running Linuxcnc 2.7.4 on that original Ubuntu install. Sometime I should plug in the current live iso and see how it runs there.

Edit:
I just took a USB drive with the Linuxcnc Wheezy image on it out to the machine and plugged it in. Short term Latency times were about the same as I had with Ubuntu 10.04.

Last edit: 05 May 2016 17:11 by Todd Zuercher.

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

JimS
Offline
Junior Member

06 May 2016 11:44 #74295 by JimS

Replied by JimS on topic Dell Dimension 3000 latency issues

Ok. I loaded 10.04 and updated to LinuxCNC 2.7. My latency is MUCH better - to the point of being usable at 25,000. But I would like to reduce it more since my driver is microstepping and I have motor reductions. I see numbers under 10,000 at the start that then jump up. What are my next steps? I have read the warnings about messing with SMI. How do I know, or at least have good guess that breaking my PC is unlikely?

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

Time to create page: 0.108 seconds